They began to think about what use could be ______ such materials.

China’s New Food Act provides for a foodrecall systemto producers have to stopproductiontheir food isn’t up tostandards.

He is a deep thinker _____ opinions are worth much.

You should try to _____ the problems by yourself. You are not a child any longer.

―What do you want to be in the future, John― I want to be _____ fashion designer. It is ______ interesting job.