Correct Answer: diminish

Solution : The correct choice is the second option .

" Increase " means to make something larger or more extensive, while " diminish " means to make something smaller or less extensive. Therefore, "diminish" is the antonym, as it represents the opposite action—reducing or decreasing instead of increasing.

The meanings of the other words are as follows:

• Widen means to make or become wider.
• Expand means to make or become larger or more extensive.
• Collect means to gather together, to accumulate, or to bring together.

Therefore, the right answer is "diminish".