Question

Fill in the blanks with the appropriate option:
Since you have been working for hours, you __________ tired.
a) Must be
b) can't be
c) must have been
d) might have been

Answer 1

Hint: The given question is a question of tenses, so we have to see what tense has been used in the first part of the sentence. The tense used is present continuous tense because of the usage of the phrase you have been working which signifies that the person has been working for quite some time. So, we have to find out which tense is to be used to signify that the person after working for hours, is tired.

Complete answer:
Option a is the correct answer because you must be tired is present tense and is in consonance with the already used tense.
Option b is wrong because it makes the meaning of the sentence wrong. After working for hours, a person is bound to be tired so you can't be tired is wrong.
Option c is wrong because you must have been tired signifies that an event that has happened in the past is being talked about now. That is not the case and so it is the wrong option.
Option d is incorrect because once again you might have been tired implies that the person is no longer tired now. In reality, the person is actually tired now so we have to use the present tense.

Note:
Always check the given sentence for the tense already used. Accordingly, you have to figure out which tense is to be used in the given blank. Always use the other options as well in the sentence to see which is most appropriate.