Correct Answer: The final problem in a series of problems that makes the situation intolerable

Solution : The correct choice is the fourth option.

This idiom is derived from the proverbial expression "the last straw that breaks the camel's back," where each additional straw contributes to the burden until the final one causes the camel to collapse.

In a broader sense, the last straw refers to the last in a series of events or issues that, when added to the previous ones, makes the entire situation unbearable or intolerable.

Therefore, the correct meaning is the final problem in a series of problems that makes the situation intolerable.