— Do I have to sell my old computer? It almost stops working.

— You ________ do so, it only needs ________. Something has gone wrong with it.

A．mustn’t; to repair

B．can’t; repairing

C．needn’t; repairing

D．may not; to repair

指出食品中有害物质的分类以及产生的主要途径，说出食品有害成分对食品安全性的重要影响。