Mary used to ________ to work, but she is used to ________ to work now.
A:riding a bike; taking a bus
B:riding a bike, take a bus
C:ride a bike; taking a bus
D:ride a bike, take a bus
下列语句是对学习的苦与乐的描述,其中描述学习为乐事的语句是( )
自然数中按是不是2的倍数可以分两类,一类是2的倍数,一类不是2的倍数.是2的倍数的数叫什么数?不是2的倍数的数叫什么数呢?