The correct answer to number 1 will depend on jurisdiction. In most jurisdictions the answer will be “D. Only the factory warranty will be honored,” but some jurisdictions limit or disallow disclaimers of the implied warranty of merchantability, making the answer “E. None of the above.” 
But the question isn’t what “what will the legal effect of this clause be”; it is “what is the writer of this clause trying to communicate” (or perhaps obfuscate).
Taking it as read (for pravnik’s benefit ;)) that the language in the quiz questions is valid in the relevant jurisdiction(s), I didn’t find them at all difficult to parse, despite having no background in law. That said, a lengthy document in that kind of language would be a pain to wade through.
The problem–as I believe I’ve said on the boards before–is that legalese looks like English, but isn’t. In reality, legalese is more like a programming language, designed to be run on the “computer” that is the court system. It’s full of terms of art that have meanings only loosely connected to the current English meanings of the same or similar terms. This is partly because, like a programming language, legalese requires more precisely-defined and rigid meanings. The syntax is locked down, because a law or contract can remain in force through all manner of shifts in English. The difference, of course, is that non-programmers don’t expect to be able to read program code; sure, they can probably recognize a few English-looking words here and there, and maybe even figure out what some higher-level functions do, but they generally don’t feel cheated when they can’t figure out a complicated bit-twiddling subroutine. Legalese tricks them, though–the words are familiar, and they can parse enough pieces that it seems as if it should all be understandable, but without a few crucial definitions, they get into frustrating tangles.
I don’t know if there’s a good fix for this. The terms of art are necessary, to some extent, although there’s certainly some obfuscation that could be pared away. They can’t really be updated, either–it would make a hideous mess of old laws and contracts, and it wouldn’t help for long, anyway. Providing “plain language” translations will help in most cases, but there will inevitably be conflicts between the legalese and the translations in some cases, which will make people even more frustrated.
Maybe it would be worthwhile to expand school civics courses to include a section on legalese–a vocabulary unit or two on the most common terms of art, more details on how courts work, and things like that. Almost no one would learn or retain enough to be able to read legalese for themselves later, but the exposure might help them understand why it’s so hard to follow.
At last someone has found a use for those graduating with liberal arts degrees!
Now that hurt.
4/4. I am a lawyer. I can see how some of these would be confusing, especially the ones that are heavy with terms of art. When that’s done in a consumer product warranty context (as it is in questions one and two), it’s a little sleazy, I guess. But, the third example appears to be from a will that sets up a lifetime trust and the fourth from a statute governing limitation of actions. Should these sort of things be written on an everyman level when to do so you actually risk compromising clarity, albeit calrity through the use of technical language? If so should I demand the medical profession adopt a similar approach to terminology?
I agree with this. IANAL, but I know that every contorted phrase is to nail down a loophole that some lawyer has found and some judge has agreed with. Incidentally, I didn’t even find that quiz hard. The phrases all said just what the answer said, but in a wordier language. Maybe it is from reading mathematics that I can parse them. Yes, I wish it was possible to be clearer but as long as we have clever lawyers and dumb judges (including on SCOTUS) this language will be needed.