通常情况下,由and连接的两个主语从句,意思都是紧密相联的,当做一个整体,谓语动词用单数。
如:What caused the fire and what was the loss is unknown.
由and连接的两个主语谓语动词怎么
用 and 连接的两个名词一般为复数念,用are/were。但是, and前后两个名词统指或同属、同构成一个人、 事物时就是单数念,用is/was。
例如: 
The worker and engineer is from Shangdong province. (工人工程师)
The secretary and the political commissar have agreed to be present at the meeting. (书记和政委)这里就是两个人所以用have
例句:
And that she did not forget her mother and always kept her home in England open for her,if Hester should ever want it.
翻译:她一直惦记着母亲,如果赫斯特乐意的话,珍珠在英格兰的家永远准备迎接她的母亲
that 在这里的用法是“用于强调先前表达过的词或短语的意思”,其前的 and 用于承前启后。and that 在此可翻译成“而且”。