如图所示，一根均匀的细木棒OC，OA= $\frac{1}{4}$ OC，B为OC的中点，在C点施力将挂在A点的重为180N的物体匀速提升0.2m，木棒的机械效率为90%，这里的木棒是一种简单机械，称为____，提升该物体做的有用功是____J，木棒重为____N（不计摩擦）．

—Yao Ming. I think he has a(n)________ for basketball.

   Bob is six years old．He is old enough to go to school． On the first day，his teacher taught him three words，“I，you，he”．Then the teacher said，“I am your teacher．You are my student．He is your student. He is your classmate.”When school was over，Bob went home. His mother asked him，“What has your teacher taught you today?”Bob said with a smile，“Listen，Mum and Dad，I am your teacher．You are my student．He is your classmate．”His mother said，“No，dear．You’re wrong．”Then she said，“I am your mother．You’re my son．He’s your father．”The next day，Bob’s teacher asked Bob to make sentences with “I，you and he”．
Bob stood up and said，“I’m your mother．You’re my son．He is your father．”All the students in Bob’s class laughed．