A.when; knocking | B.when; knock | C.that; knocking | D.that; knock |
A.Before | B.When | C.Since | D.As |
A.while | B.if | C.when | D.whether |
A.when | B.until | C.while | D.before |
A.how | B.who | C.where | D.which |
A.what; that | B.that; that | C.that; what | D./; that |
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