There being no witness on the spot, the police were delayed by the _____ of information about the crime.
—Did you look up the time of trains to Shanghai? —Yes, the earliest train is________ to leave at 5:30 am.
She stepped into the bedroom quietly_______ she might wake up her roommates.
Many people have been ill from a strange disease these days,________ we’ve never heard of before.
—He_______ to the meeting. Have you informed him of it? —Sorry. I________to.
It is not enough only________ the rules of grammar if you want to learn English well.