One day, it was cloudy. An old man together with his grandson were waiting for the bus at the bus stop. Beside them stood a school boy with a umbrella in their hands. Before long,  it started raining and then it began raining hardly．The old man and his grandson began to run because the sudden rain. Seeing that,  the school boy hurried to help them, shouted to them, “Don't run, Grandpa, and you will fall down. Let's shared the umbrella together.”With these words,  he held the umbrella over the old man and the little boy. It was not long since the bus came and they get on the bus together.

劳动和偶那个的必备条款有

A.劳动合同期限 

B.工作内容 

C.试用期 

D.保密条款