A sentence with one blank is given, indicating that something has been omitted. Choose the word that best fits the blank appropriately. You will have to undergo a _______ of tests before the interview.

The trick here is to follow the structure of the statement. The blank is followed by 'of' and thus the blank will take a filler that can be followed grammatically by 'of' and also manages to give a proper meaning. On the basis of these filters, none of the options except option 2 makes any sense.