补全句子
（1）这孩子费了很大劲计算那道数学题
The ___ had problems ___ ___the math ___.
(2)Sam已连续滑冰两小时,对吗?
Sam ___ ___ ___ for two hours,___ ___?
(3)老师鼓励我们对理科感兴趣
The teacher ___us ___ ___an___ ___science