________my mother is very tired after a whole day's hard work, she tries to spare time for me.
A：Every time
B：Whenever
C：Even though
D：As
某同学骑自行车下坡滑行时，速度越来越快，下列说法错误的是（）
正数x、y满足x+2y=1，则xy的最大值为（ ）
