سوال ۲ کنکور ارشد علوم کامپیوتر ۱۳۹۷

The blank needs a verb meaning to make a problem less severe / reduce its impact. Applying lime and organic fertilizers eases the low-soil-fertility problem.

• mitigated = made less severe, alleviated — fits perfectly: the fertilizers reduce the problem.
• traced = followed/found the origin of — wrong; you do not "trace" a problem by fixing it.
• preceded = came before in time — illogical here.
• necessitated = made necessary — the fertilizers do the opposite; they relieve, not require, the problem.

So the answer is (3) mitigated.

Exam trick: When something solves or lessens a problem, the verb is usually mitigate / alleviate / reduce, never trace (find the cause) or necessitate (cause a need).