Explanation:

Correct Answer is (e).Everyone must have heard this popular motivational saying, “When the going gets tough, the tough get going.” Clearly, ‘tough’ has to fill the blank.
Now, both ‘gritty’ and ‘strong’ are synonyms of ‘tough’ and therefore either of them can fill the blank too.
Evidently, any of the three words can be filled in place of the blank.
Option D is hence the correct answer.