This is the very plan for the summer holiday ______will be suggested by his cousin.

因为plan前面有the very修饰,先行词前面有only,any,few,little,no,all,one of,the same,the very等词修饰时 都只能用That
The only thing that we can do is to give you some money.
Li Ming is the only one that got full marks (满分)in our class.
Li Ming is one of the students that want to be teachers in our class.