Here are three balls, ___?

A．which one is the bigger

B．what ball is the bigger

C．which one is the biggest

D．what ball is biggest

下列说法不正确的是（　　）

A．聚乙烯塑料可用作农用薄膜

B．聚氯乙烯可用作电话卡基体

C．SO₂用于多数食品的漂白

D．KIO₃可用作食盐的添加剂