Tears help to protect the eye from potentially harmful foreign bodies.

　　眼淚有助于保護(hù)眼睛去除可能有害的異物。

　　Water is not an effective shield against the sun's more harmful rays.

　　水不能有效阻擋太陽中更有害的射線。

　　Many household products are potentially harmful.

　　很多家用產(chǎn)品有潛在的害處。

　　Fruit juices can be harmful to children's teeth.

　　果汁可能損壞兒童的牙齒。

　　The drug is not harmful per se, but is dangerous when taken with alcohol.

　　這種藥本身無害，但與酒同服就危險了