. It is important to know exactly the message ________ and ________.

A．you want to send it to people; that you try to get them to do

B．sent to people; what do they want to do

C．you want to send; which you want people to know

D．you want to send to people; what you are trying to get them to do

两个大小相等的力，当它们的夹角为90°时，合力为F，则这两个力的大小为       N，这两个力的合力最大值为　　　N。