So a key difference between a rocket and a jet plane is （） a rocket’s engine lifts it directly upward into the sky, whereas a jet’s engines simply speed the plane forward so its wings can generate lift.

So a key difference between a rocket and a jet plane is （） a rocket’s engine lifts it directly upward into the sky, whereas a jet’s engines simply speed the plane forward so its wings can generate lift.
A.that
B.why
C.where
D.how
正确答案：that