---Monitor, is ________ in the classroom?--- No, Lily is out.
There _____ a pen, two pencils on the desk.
—Lily, here are your pens. Please _____.—OK, Mom.
I don’t like physics ______ it’s too difficult for me.
—_____ do you _____ the book?—It’s very interesting.
—How long can I keep the books?—_____