Nothing. Their duty is to guard the tomb and there should be no reason at all to when they stop. When changing guards maybe but someone is still there watching.
I believe the pronoun in this sentence is <u>your key</u>.
After school we planned to do homework and
swimming has no error. The correct answer between all the choices given
is the last choice or no error. I am hoping that this answer has satisfied your
query and it will be able to help you, and if you would like, feel free to ask
another question.
