I have to disagree with the answer. I ran the code on SQL server 2005 and got the following output:
abcd
4join14join2
4join14join2
2join32one
2join32one
1oneNULLNULL
NULLNULLNULLtwo
NULLNULLNULLthree
As I had worked out the same output before running and answering the question I decided that A, B, D and E could not possibly be correct so went for C as the only remaining option.
What have I missed?