This year the farmers were just able to gather in the _____ before the fine weather came to an end.

A：collectio

B：harvest

C：flower

D：plant

小军用如图乙的实验装置进行实验，将20克稀盐酸加入到1.25克样品中，生成的CO₂体积与反应时间的关系如图丙。已知本实验条件下CO₂的密度为1.8克/升，求该石灰石样品中CaCO₃的质量分数。