Select the most appropriate option that can substitute the highlighted segment in the given sentence.
Despite the company's initial setbacks, they decided to increase their commitment and invest more resources in the project to ensure its success.

Correct option is D

Option (d) "double down" is the most appropriate option to substitute the highlighted segment. The phrase "double down" means to increase one's effort or commitment, particularly in a challenging situation, which fits well in the context of the sentence.
Correct sentence: Despite the company's initial setbacks, they decided to double down and invest more resources in the project to ensure its success.
Explanation of other options:
· Double trouble (a): Refers to a situation with twice the amount of trouble or difficulty, which doesn't fit the context.
· Double agent (b): Refers to a spy who works for two opposing sides, which is irrelevant in this context.
· Double back (c): Means to turn back or retrace one's steps, which doesn't fit the meaning intended in the sentence.