The trees ___front of the house are ___the charge of Mr. Li.
___ you lose the paper document, sign in www. Sina.com, __ you might download all you need.
When you read the book, you’d better make a mark _____ you have any questions.
The child tiptoed quietly to the bird. ______ into the forest when he was about to catch it.
He _______ busy yesterday, or he _______ you with your experiment.
A teacher of English and class teacher _______ us something about volunteer workers.