Are you sending the invitations early enough（ ）the people invite

Are you sending the invitations early enough（ ）the people invited will have sufficient notice to respond?
A、such that
B、so that
C、in order to
D、while
【正确答案】：B
【题目解析】：你的邀请函是否发送的足够早以让受邀人有时间回复？