One of the children must have hidden it up.这是现在完成时吗?这个have仅仅是助动词表完成的意思吗?如题.会不会是其他的用法?

one of the children kicked a ball very hardone of the children,为什么不说one children Children of the world are all like one. Children of the world are all like one. one for each of the children.what mean is it? the odds of children for children,the important one is that of receiving gifts.其中OF是什么用法和意思? One of the children are sitting near the door.什么意思 One of the children ( ) sitting near the door.A.is B.am C.are One of the children-------under the apple tree A are B is A am D be baseball one of the most f_______ sports in America.Children play baseball in sports f_______or inparks For children,the most important one is that of receiving gifts.这里that是干嘛的. one of two children born at the same birth（a noun） children of the world are all live one的汉意 one-second 还有two-third又是什么意思?有a half of the children 这种说法吗 THE CHILDREN OF LIGHT AND THE CHILDREN OF DARKNESS怎么样 CHILDREN OF THE ALLEY怎么样 the fourth of twelve children The Grandmother of my children