Question

Because he didn't know how to do it，he went to her for help. _____ _____how to do it，…….

可否直接用Didn't know how to do it,…… .
还是Not knowing how to…….
Because he didn't know how to do it，he went to her for help.
句型转化为 _____ _____how to do it，…….

Answer 1

正确的是：Not knowing how to do it, he went to her for help.
如果用don't know how to do的话，句子有明显的语法错误，因为don't know 和 went to 都是谓语，而一个句子中不能有两个谓语，所以必须把don't know改为非谓语的形式:not knowing.
如果一定要用don't know的话，句子可以是这样:
He doesn't know how to do it, so he went to her for help.
用一个so 或者 and 等连接词来连接两个完整的句子。

Answer 2

第一个 要在后面句子加连接词