某市在一次扶贫助残活动中，捐款约3180000元，请将3180000元用科学记数法表示为(  )

根据短文理解，选择正确答案。

    The size and shape of your ears show your character more than any other part of the face. Other parts of the face change shapes as we get older, but ears do not change their shape. They only change in size.

    Reading people's character from their ears is a very old science. In the past people thought that a person's ears with colour was dangerous. They also thought that the shape of the ears showed if a person was musical or not. Today, too many people believe that the size and shape of the ears help you know if a person is musical.

    Ears are all different, and each different thing has a meaning. Next time you look at a person, see if his or her ears are large, medium-size, or small. Look at the lobes（耳垂）. Do they stick to the face? Ears that are always red mean that a person may get angry easily. Ears that are always cold and nearly white colour mean that a person has a nervous(紧张的) character.