A:2x2﹣4x
B:6x2﹣24
C:﹣4x2+16
D:4x2﹣16
①葡萄糖 ②蔗糖 ③胰蛋白酶 ④DNA.
-- What's the rocket used____ (to / for)?
--Oh, it's used to send satellites or spaceship into space.