He was brave enough ___________ for the school volleyball team and succeeded.

We are _______ by doctors to eat more natural food and take plenty of physical exercises . [ ]

The Mekong River Commission has found no evidence ______ the dams on the upper reaches have an influence on the water flow downstream

In Hong Kong the eighth day of the fourth lunar month is a special day, called Bun Festival, ______ many residents and travelers gather at Cheung Chao island to celebrate a unique tradition.

Have you seen Bill recently — Oh, no! Nobody knows ______ he is! Everyone is looking for him.