One of the first foreign expeditions _______ MountQomolangma arrived in Tibet in 1921.

The coats are 200 dollars each, but______we offer a discount of 30%, you’ll get one for only 140 dollars.

You must trust him; he is a man who _________ his promise.

下列各句中加线的成语使用正确的一项是(　　)

Knowing their son failed in the exam, the parents stood there, ________.