I think you jump very high,此处jump为什么要用原形?是I think （that）+ 从句

I think you jump very high,此处jump为什么要用原形?是I think （that）+ 从句 I think you jump very high. (改为否定句) you jump.i jump You jump,I jump! sometimes i jump into bed```` just to think about you you jump I jump;I jump you must jump I don't think the dog the hoop jump over jump through jump a You jump I jump,I jump You can't dance. If you jump,I jump,Now I jump,And you? I CAN'T JUMP VERY HIGH改成肯定句 you jump i put you jump. i jump you jump是啥意思呢?