After the trainer was sure that the whale could look after itself, he _______ it into the sea.

The army officer _______ his men to fire as soon as the enemies came up.

Heads from different countries gathered in Amsterdam and President Xi jinping _____ a speech on nuclear safety.

The graduation ceremony, which thousands of graduates _________ last night, was a success.

—Was he still there when you were away to answer the phone?—There is no doubt about it, but he ________ soon afterwards.