It remains _______ whether the medicine will work on human body. [ ]

a, the founder and chairman of China’s Alibaba Group, has a $28.6 billion fortune, ______making him the richest person in China.

Those who know how to ________ others can naturally lead a happy life.

This picture was taken a long time ago. I wonder if you can my mother.

．piano is her main focus，she’s also great at guitar