【单选题】Teachers recommend parents __________ their children under 12 to ride bicycles to school for safety.
【判断题】Under a bareboat charter,the charterer takes over almost all of the shipowner’s functions.( )
【单选题】若证券A与证券B的相关系数为0.5,则两者之间的关系是( )。
【单选题】人血清中含量最高的是哪种补体成分 A.C1~C9