五线谱有两种唱名法： 固定唱名法和（）唱名法。
参考答案：首调
影响产前发育的因素有__________、__________、__________、__________、__________、__________。
—Must I tell John the news —No, you ______。 I've told him already.
A. mustn'tB. wouldn'tC. shouldn'tD. needn't
