-It is correct to say :
She arrived late for the meeting , which was annoying.
Here “which” is a relative pronoun that means “She arrived late for the meeting “ .You can not use “what” in this sentence .
- You can use “what” in this way :
1. What she had done annoyed me .
2.I came to see what she had done .
=> “What”is used before a noun –clause .
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