Question

Fill in the blank with the most appropriate word:
A: You bought the tickets, didn't you?
B: No. I _____________, but I didn't have enough money.
a) Couldn't
b) ought to have been
c) was supposed to
d) might have

Answer 1

Hint: This is a dialogue between two people where one of the persons is asking another person if he has bought the tickets and the other person replies that he did not because he didn't have enough money. Person B says that there was a chance he could have bought the tickets but he could not because he didn't have enough money. Using this clue find out the correct option.

Complete answer:
Option a is wrong because using the word but means that the first part of the sentence should be in contradiction with the second part of the sentence. If you use the word couldn't in the first part, there is no contradiction if we say that he couldn't buy the tickets because he did not have enough money.
Option b is wrong because I ought to have been means that he himself should have been the tickets which obviously does not make sense and thus the option is wrong.
Option c is wrong because if we say I was supposed to, it means you're informing the person that you are supposed to buy the tickets but you could not buy it because you did not have enough money. But in the given question, we can already understand that person A knows that person B was supposed to buy the tickets so there is no question of informing the person that you are supposed to buy the tickets.
Option d is the correct answer because it says I might have bought the tickets but I could not buy them because I did not have enough money, therefore, we are fulfilling the criteria of using a positive first part of the sentence followed by a conditional conjunction, after which we are using a negative part of the sentence.

Note:
Students might be confused between options c and d but as already explained above, was supposed to mean we have to inform the person but since in the question, the person is already informed, there is nothing to inform the person. Thus option d is the correct answer.