— Do you know if we will go for a picnic this Saturday?
— I think we will if we ________ any classes.
A:won't have
B:didn't have
C:don't have
D:aren't having
4角改写成用元作单位数是____元。
侦察兵为及早发现敌军骑兵的活动,常把耳朵帖在地面上听,就能判断附近是否有敌人的骑兵,下列解释错误的是( )