Answer:
21.
Signal word: since
Cause: The picnic was canceled
Effect: The rain is coming
22.
Signal word:For
Cause:David could not attend the ball
Effect: He was sick
23.
Signal word:Because
Cause: John was lazy
Effect: he did not pass the test
24.
Signal word: If
Cause: The dress is on sale
Effect: She will buy it
25.
Sigbal word:When
Cause: The host was surprised
Effect: We arrive early to the party
I hope this will help you
