You must be firm ( )you think yourself to be right.括号中为什么用wh
You must be firm ( )you think yourself to be right.括号中为什么用where而不是on which Each boy and girl who (are )to visit Hengshui Middle School in Heibei Province ( is ) asked to be at the bus station at 6:30.括号里的be动词为什么单复数不同?