My sister often ______ gift, but she doesn’t ______ them.

A．receives, accept

B．receives, accepts

C．accept, receives

D．accepts, receives

取一根用砂纸打磨干净的镁条和一个石棉网，将他们一起放在托盘天平上称量，然后在石棉网上方将镁条点燃，镁条燃烧时发出耀眼的白光，产生大量白烟，再将镁条燃烧后的产物与石棉网一起放在托盘天平上称量，发现质量减轻了。有同学据此认为“质量守恒定律不是普遍规律”，这种说法对吗，为什么？