Hawkwood and his men would march into a city-state and, after burning down a few farms, would offer to go away if protection money was paid to them.

这句话里and后面加逗号是什么用法？would是和and连接在一起的吗？

这句话里burning down改成burning可以吗？

if和that用法是不是都是从句？

【答】

1. 这句话里and后面加逗号是什么用法？would是和and连接在一起的吗？

——would march into a city-state 和would offer to go away，是两个并列的谓语。由于第2个谓语前加了这个介词短语after burning down a few farms，这就需要停顿，所以，这个介词短语两端都需要加逗号。如果没有这个成分的话，就是这个样子：

Hawkwood and his men would march into a city-state and would offer to go away.

2. 这句话里burning down改成burning可以吗？

——不可以，意思不同。burn表示“动作”：（使）燃烧；加上down后，表示“结果”：烧毁。

3. if和that用法是不是都是从句？

——if 引导条件状语从句；that也可引导状语从句，但主要引导名词性从句。