Choose the closest paraphrased version after each of the followi

Choose the closest paraphrased version after each of the following sentences or the italicized part.
Essentially, I am putting together a huge jigsaw puzzle. The edge pieces are in place and various areas are getting filled in, but pieces are missing.
A、…I am trying very hard to complete the complicated work.
B、…playing jigsaw puzzles is helpful to complete the work.
C、…I play jigsaw puzzles in my spare time to relax myself.
D、…challenging tasks call for joint efforts of many people.
【正确答案】：A