There is nothing nonsensical or hard to understand about what you are saying there. What is nonsense is your previous statement that the explanation says this. It doesn't. The explanation says that the result is truncated to the length of the check expression (implying that the length of NULL is 5 here). That is NOT remotely the same thing. Why do you want to claim it is?

I'll skip most of the rest of your comment, because anything I said would be much the same as before, so pointless repetition: a waste of space; but on a couple of things it may be worthwile to say something.

The best you've offered is a pointer to the general statements that functions determine the results of their results. That doesn't actually tell me a single thing about what left determines as the type of its result. I'm pretty sure that this is NOT documented in BoL - sure enough that I'll waste no more time looking for it. It's quite clear from its behaviour on a few test cases that it makes no use any type information available for its first argument other than to place an upper bound on the length component of the type of a NULL and to determine whether the character component is char or nchar, so what do I need documentation for? Oh, it might change in the next release if it's not documented - well, hard luck me).

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Clever piece of selective quoting there, sir, a nice "..." conceals the words that make nonsense of your remark about whining about the answer by stating clearly and unambiguously that the answer is correct. You know perfectly well that this discussion has nothing to do with the answer, but concerns the explanation. Why pretend it has?

As to number of people, we first have abrar asking for more explanation (which is part of why I commented - and his reply to my comment suggests he found it useful) and sknox saying he thinks the explanation is inadequate and making much the same points as me in a looser style. So that's 3 people on one side. On the other side we have one liners from Jason and Ramchandra, a two-liner from yoursel (quibbling that the absence of a NOT NULL constraint was not explicitly declared - now that really is whining about nothing, isn't it) and a comment from dbowlin. That's 4 people. We don't have the usual collection of whiners claiming it's not fair they didn't get their point, because there is nothing anyone could hang such a claim on - as I said before, the question is clear and unambiguous and the answer is correct. So it's 3:4 - not a startling majority either way, is it? Or is that a grey area that you want to claim is white?

My comments are fourfold:

(i) I chose the wrong answer (not because there's anything wrong with the question but because I didn't know that the type of the result of left(cast(null as varchar(50)),5) is varchar(5) - I should have known, but I didn't).

(ii) It's a good clear question with a good correct answer.

(iii) The explanation is incorrect (only the type of the check argument affects truncation of the result, not its length) and incomplete (no mention of the type of the result of the left function).

(iv) I find the behaviour of the left function surprising and consider it not consistent with the behaviours of arithmetic functions, which have the advantage of being well documented.

Do you actually disagree with any of these, or are you just having fun?