Which is correct?
A. Nobody deserves to have their life threatened.
B. Nobody deserves to have their lives threatened.
A) is correct.
Nobody is singular, their is plural. The only acceptable choice when I was in college would be “Nobody deserves to have his life threatened.” “Their” used with “nobody” would have doomed an essay to no higher grade than a B.
Well, it’s going to depend. I would happily roll with A. Someone who doesn’t dig the singular they would probably not choose either sentence.
Nobody is a singular pronoun. It shouldn’t be used with the word “their”. Technically both sentences should say “Nobody deserves to have his or her life threatened.”
However, there are many people who favor the singular version of “their” to refer to a neutral gender. If you want to use “their” instead of “his or her” then I would use “life” instead of “lives”.
Thanks - the disconnect between “nobody” and “their” was throwing me off, but I couldn’t figure out why. The lack of a gender-neutral singular pronoun in English is most blowful.
Would it be any different if it was “no one” instead of “nobody”? Or is that the same?
English is my second language, so I’m sure there are a number of subtleties I don’t quite get.
Including Bill Shakespeare, which I think you’ll find makes it bona fide legit Englishing ! 
(seriously though, it’s one of those grammarian trench wars. I don’t want to get in there.)
It’d be the same. Nobody, no one, zero, no, etc… all call for the singular for a relatively logical reason (which is unprecedented in grammar rules ! :p) : if there is less than one, it can’t be plural, can it ?
Ah. Thank you!
To quote Victor Borge. “It’s your language, I’m just trying to use it”
There is one. They/them/their. That some people do not recognize this function points out a lack of knowledge on their end rather than a deficiency within English.
Utter nonsense, unless the teacher was an imbecile.
No English teacher worthy of the title would lower a grade so much over so small a thing, even if they (and, yes, the use of “they” and “their” as single, indefinite pronouns has a long and accepted lineage) had been incorrectly educated on the issue.
You are remarkably optimistic about the linguistic acumen of the average english teaher.
It is an absolute certainty that in any language thread a post starting “my high school English teacher said…” will be dead wrong.
For most of the last century, this was one of the greatest no-no’s, much more important than not ending a sentence with a preposition or splitting an infinitive. It was verboten, period. English was taught as prescriptive, and you were proscribed from doing this.
It would be nice to hear that English teachers today are not enforcing this distinction, but you know nothing about history if you think this used to be true.
-A former prescriptivist.
Apropos - I saw this article that I found quite interesting: 10 grammar rules you can forget: how to stop worrying and write proper | Language | The Guardian
I’d love to hear your take on this (now that the OP has been answered and all)
Ain’t that the truth.
Were I writing for a composition, I would either ask the teacher if they permit the gender-neutral singular use of third person plural pronouns and, if not, I would go with the awkward and needlessly wordy “his or her” construction. When I was in college in the 90s, I saw a few books take different ways of working around this, including the schizophrenic “alternating” pronouns (sometimes within a paragraph between sentences, sometimes between paragraphs), i.e., masculine would be used as gender neutral, then feminine, then masculine, etc. It made for irritating reading. And don’t even get me started on those invented third-person pronouns like ze/hir/hirs.
IMHO, “their” is the best solution, but it’s not 100% accepted in academic/formal writing.
So if I have no apples, I should say I have “no apple”, not “no apples”? 
I think anything other than exactly one calls for a plural. Even negative 1.
[QUOTE=Cecil Adams]
There has been progress on one front: the use of “they,” “their,” “them” as third-person singular with indefinite constructions such as “anyone,” “somebody,” “each,” “the person who,” etc. This produces sentences like “Somebody has forgotten their hat,” which purists find offensive. However, as sociologist Ann Bodine points out, singular “they” was in wide use by distinguished writers of English prior to the attacks of 19th-century grammarians, and its use in speech has persisted to the present day. Not only does it fill an obvious need, it has a precedent in “you,” which long ago supplanted second-person singular “thou.” Cecil will go so far as to predict that within a couple generations singular “they” in many instances will be acceptable in formal written usage.
[/QUOTE]
[QUOTE=Merriam-Webster]
…
<and every one to rest themselves betake — Shakespeare>
<I would have everybody marry if they can do it properly — Jane Austen>
<it is too hideous for anyone in their senses to buy — W. H. Auden>.
The plural pronouns have also been put to use as pronouns of indefinite number to refer to singular nouns that stand for many persons
<'tis meet that some more audience than a mother, since nature makes them partial, should o’erhear the speech — Shakespeare>
<a person can’t help their birth — W. M. Thackeray>
<no man goes to battle to be killed. — But they do get killed — G. B. Shaw>.
The use of they, their, them, and themselves as pronouns of indefinite gender and indefinite number is well established in speech and writing, even in literary and formal contexts. This gives you the option of using the plural pronouns where you think they sound best, and of using the singular pronouns (as he, she, he or she, and their inflected forms) where you think they sound best.
[/QUOTE]
Nicely descriptivist. (At least they didn’t go berserkly post-literate as they did with “literally.”)
Nobody deserves to have one’s life threatened.
Grammatical non-sexist correction.