✨ ベストアンサー ✨
The woman.
Subject is waiting
Who becomes the subject pronoun while the woman becomes the modifier.
The woman who is waiting ...
What ... you to do such a foolish thing?
Cause to do
Do is the second verb in this sentence so it takes to in front of it.
Cause
What causes? = Why is ...?
What caused you to do ...?
Why did she study so hard?
Because she wants to pass the test.
So that she can pass the test.
To pass the test.
For passing the test.
She studied so hard (use one of the above ideas) she could pass the test.
So that explains why and is used to add a complete thought after the first complete thought without ending the sentence.
Because is usually an add on to a complete thought and is not considered a complete sentence. It is bad form to start a thought with because.
For + noun only is used to answer why
To + verb only is used to answer why.
ありがとうございます！