16.You can’t imagine that a well-behaved gentleman__________be so rude to a lady.

While traveling in a strange place, you’d better _______ the local people and follow their customs (习俗).

How long have you__________ the book –For three days.

He________ his experiments and made a great contributionto our country.[ ]

______ really makes “Gangnam Style” popular is not the lyrics, but the part of “Horse Riding Dance”.