题干
—My grandma looking at that photo on the wall.
—I can understand. It helps her remember her childhood.
A：enjoys
B：enjoyed
C：was enjoying
D：will enjoy
答案(点此获取答案解析）
A
，据市场分析每辆客车营运的总利润
y(单位：万元)与营运年数x(x∈N)为二次函数关系(如图)，则每辆客车营运多少年，其营运的年平均利润最大（ ）
