题目

Daniel sometimes plays _______ basketball after having _______lunch.A. the; an B. the; a C. /; / D. /; the 答案：【答案】C【解析】句意：Daniel有时午饭后打篮球。根据体育器材前不加冠词the，排除A/B；根据have+三餐，吃早饭/午饭/晚饭；故选C定义一种运算“*”，对正整数n满足以下等式：①1*1=1；②(n+1)*1=3(n*l)，则n*l=    (    )A.3n             B.3n-1             C.          D.