Look _______ my summer vocation plan. A. at B. in C. on
Even the top students in our class can't work out this problem. So it _____ be very difficult.
This machine is very easy to use.______ can learn to use it in a very short time.
One of his friends ______ his daughter sometimes.
The game is _____ funny that many of them like it.
Are there _____ trees behind the house?