How many ________do you have? A、math books B、math book C、a math book
( ) 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?