根据下列句子及所给汉语注释，在句子空缺处写出各单词的正确形式（每空只写一词）。

1. Wood has been used to make paper since the 19th __________(世纪).

2. He got up __________(早) than I did this morning.

3. Sam __________ (遇见) Mary in England and visited her school.

4. A nice hot bath should help to __________(放松) you.

5. They're __________(计划) to go to Beijing at weekends.

若操作温度不变，精馏塔设计压力增加，则塔顶、塔底产品组成（）

A.塔顶变重，塔底变轻

B.塔顶变轻，塔底变重

C.塔顶、塔底均变轻

D.塔顶、塔底均变重