Question

SAT语法问题，求解答！

1.When Mr. Ruiz arrived at the holiday sale, she realized that she had left her wallet at home and （must go） back to get it. No error 括号里哪里错了？

2.When Dr. Jantos speaks, she does not attempt to impress her （listener with her speaking）. 括号里哪里错了？

谢谢！
为什么要had to go? must go不行?
must不能用在过去式？

Answer 1

1 must 只有一般现在时和过去式 用 had to do强调客观因素导致（钱包掉家了）不得不回家。must是主观上或规定导致。比如会友间接电话，说一句i have to go
交通上 When the traffic light is red,you must stop.
2 对比一下
Our teacher impressed us with the importance of industry and economy.
老师要我们牢牢记住勤奋节俭的重要性。
给...极深的印象;使感动[W][H]
I was very impressed by his story.
他的故事深深打动了我。

Answer 2

1. had to go
2. with her speech

情态动词must无过去式, 如需，可用had to

Answer 3

第一题当中的 realized 决定了从句需用过去时，所以，must 应该为had to.
第二题当中的speaking 作定语如，speaking skills, 作名词时是说话，强调动作，而speech 侧重指言辞 如，we express our ideas by speech.