I saw that video.
It’s a present progressive verb. The water is boiling. The verb is “is boiling.” Same with “he is running.”
And to the OP, sentence A is the better sentence. I was taught to avoid sentences like, “the water is being boiled” if you can help it. And in this case it’s ok because water boils.
Who boils water in the oven? (unless it is a microwave oven, in which case, it would be “could you turn the microwave off”).
That must be where Uncle Albert is from (I knew I knew it from a lyric, but had to google to see just what).
C. “The water’s aboil.”
I think it’s just ambiguous. I can’t think of any reason to analyze as exclusively the present progressive or as a copula. It can be an intransitive, reflexive usage of to boil, hence “is boiling” is the present progressive. Or it can be a copula, where “boiling” is an adjective describing the current state of the water, and “is” is a linking verb.
To convey the difference, I would have to use something less ambiguous, like “The water is boiling hot,” or, yes, “the water is being boiled.” Otherwise only context can tell the difference.
In the very second post Jeff Lichtman mentions one of the common meanings of the verb boil, which is, “to become so hot that bubbles are formed in a liquid and rise to the top,” (and which actually is more common than the other meaning), and in the third post I point out (and Hari Seldon repeats later) that there is class of verb in which the patient effectively becomes the subject of the verb. I gave examples of some other verbs in this class (open, break). How else do you explain this sentence, *Water boils at 100 degrees.*which appears in every middle school physics text ever printed?
Thanks for your comment, but take a look at this,
Boil, (verb)
[ intransitive , transitive ] when a liquid boils or when you boil it, it is heated to the point where it forms bubbles and turns to steam or vapour
The water was bubbling and boiling away.
Any second thought?
OK, I was wrong. As a general matter of the grammar, anyway; I still think I was right in characterizing the original sentence as a statement about the condition of the water.
Thank you everyone for comprehensive reviews and comments. I appreciate all of them.
To those who object “ the water is boiling” as an appropriate phrase in below context
Mum: Hey Tim go and check if the hot water is ready.
Tim: Yes Mum, the water is boiling, shall I turn the oven off?
Please let me know what is the appropriate and the most common phrase in your everyday life expressing the Tim’s reply to his mum?
Thank you.