From earliest times their energy had gone,first of all,into earn

From earliest times their energy had gone,first of all,into earnest toil.
A、..the difficult conditions had challenged people’s endurance.
B、..the most urgent task for people was to make a living by hard work.
C、..the unpleasant physical work had disappointed people there.
D、..people were very serious about how to use their energy.
【正确答案】：B
【题目解析】：从远古时代开始，他们的能量就投入到辛苦的劳作中去了。