My father warned me going to the West Coast because it was crowded with tourists

It took him a long time to ______ the skills needed to become a professional artist.

The air pollution is terrible.- It will be worse ________ we take action to protect the environment.

Tina stayed in Tianjin for a week.She________ spent some days in Beijing.

gone out with ________ hisname–you know, the boy with the red car– Oh, it’s Jack.