A：(b-2a)mol
B：b mol
C：a mol
D：2a mol
阅读诗歌，回答问题
望洞庭湖赠张丞相
孟浩然
八月湖水平，涵虚混太清。气蒸云梦泽，波撼岳阳城。
欲济无舟楫，端居耻圣明。坐观垂钓者，徒有羡鱼情。
—What should we do for the disabled children in the Children's Home?—You're supposed to________ a study group to help them.
____的使命是维护国际和平与安全。
Zhou Yang ________ to her hometown with her parents five years ago.
