Sally said that they_____a surpise party the next dayA would have B will have C are having D have

Sally said that they_____a surpise party the next day
A would have B will have C are having D have

Sally said that they_____a surpise party the next day
said ,the next day 这两个词决定用过去将来时
而过去将来时的结构是would/shoud+动词原形

A
said表示从句是过去时。而the next day表示将来、
故用过去将来时

c

B