【题目】All the gifts must be mailed immediately________in time for Christmas.
A．in order to have received
B．in order to receive
C．so as to be received
D．so as to be receiving
在线课程【答案】C
【解析】so as to后接动词原形，表示“以便”，根据gift与receive的关系可判断出要用to be done的形式；表示被动。