Green products are becoming more and more popular because they are environmentally _________.

The boy was      at the terrible story, which was written for adults.

If you want to see Mr. Johnson on Friday morning, make sure he is ______ ahead of time. 

According to statistics, a man is more than twice as likely to die of skin cancer _________ a woman.

Though he started late,Mr.Guo played the piano as well as,if______,Miss Liu.