From Twitter
Choose:
A. Are you __?
B. Yes. C'mon, give me my sandwich and let me pay.
A. Is it __?
B. If it were an emergency would I be buying a sandwich? I have __; I'm meeting my mother-in-law; if I'm late, I die.
A. Then, hurry!

a. an emergency
b. to hurry
c. in a rush

The Answers are:
'in a rush' (c)
'an emergency' (a)
'to hurry' (b)

Explanation:
The first answer can only be 'in a hurry':
'Are you in a hurry?' ... because we wouldn't say: 'are you to hurry?' or 'are you an emergency?' These expressions do not make sense.

The second answer is easy, because the question begins with 'is it', so we know a noun is needed and 'is it in a rush' doesn't make sense, because it refers to something that has not been spoken about; so the only answer is the other noun, 'an emergency’.

The Third answer must then be (b) 'I have to hurry.' Not only is it the only answer remaining, but we can't say 'I have in a hurry.' We could say: 'I have an emergency', but this situation is not an emergency; emergencies are about physical danger or about having to go to the bathroom in a hurry.