They walked____(穿过)the forest yesterday afternoon．

初一学生李龙，平时只关心自己的学习，对集体的事情漠不关心，也很少参加集体活动。他的行为（    ）

    Tom always can't sleep well at night. But he was never late for work. He went to see his doctor on Sunday afternoon. He took the subway to get there. He met his boss on the subway and they talked for a while.

    Tom got some sleeping pills from the doctor. That night Tom took the pills. He had a nice sleep. He went to work happily on foot in the morning. Getting into the office, he said to his boss “I had a nice sleep and got up happily this morning.” “That's fine,” shouted the boss, “but where were you on Monday?”

向质量为m克的CaCO₃和KHCO₃的混合物中，加入质量分数为a%的稀盐酸n克，恰好完全反应后，得到二氧化碳的质量是w克．（已知：KHCO₃+HCl═KCl+H₂O+CO₂↑）下列说法正确的是（　　）

作者谈及青少年时期“不知口体之奉不若人也”时，运用外貌描写，分别描述了自己和“同舍生”的服饰，这是怎样的写法？他借此赠给马生的精神礼物是什么？