The reason ______ he gave for not coming was ______ his mother wouldn’t allow him to.

Pollution is a serious ___________ in China . PM2.5 has been increasing in recent years.

It was on a cold winter evening his father left home and was never back.

________and angry, Tony rushed out of the room.[ ]

________ the police thought he was the most likely one，since they had no exact proof about it，they could not arrest him.