why is "turn" not "duty"?

[Vaok]

Two problems:

1.The room is so duty and disorderly. Whose ___ is it to clean it, do you know?
A. task B.turn C.duty D. round

why can't we use duty or task here?

2.I am ___ money this week. can you lend me some?
A. lack of B. lacking for C. short of D. short for

D. is not right,but what about A and B?

would anybody give me some help?

[Mister Micawber]

.
#1--- Turn is the usual answer, but both task and duty are also OK.

#2-- A does not fit the grammar and B is distinctly odd: the phrase normally appears in the negative (not lacking for)
.
_________________
Native English teacher at Mister Micawber's

[Vaok]

Dear Mister Micawber

Thank you very much!