Can or Should

[McKinney]

Hi,

I did an exercise and my native English speaking friend said the correct answer is B and my teacher said the correct answer is C. Can you please tell me which one is correct? Here is the exercise:-

Rarely __________ have been faced with such a daunting problem.

a) a minister can
b) can a minister
c) should a minister
d) a minister should

Thank you!

[Alan]

Actually either is grammatically possible, but (b) is the more plausible answer.
A poorly designed test question!