Nice clean question.

But maybe a little too easy. If one assumes that T-SQL has the sort of consistent syntax that most programming languages have, then only the second and fourth options are possible answers (since if either of the otherw was wrong then so would at leat one more be wrong, and the radio buttons allow for only one); so the only question is whether the "as" keyword can be omitted or whether "a as b" and "b as a" mean the same thing - but letting those mean the same thing would mean one couldn't cope with renaming a column with another solumn's name, whic would be rather odd, so the principle of minimising oddity (which in my experience applies to all languages except C++) tells us the answer straight away.