题目

在一定条件下，RO和氟气可发生如下反应：RO+F2+2OH－RO+2F－+H2O 从而可知在RO中，元素R的化合价是 A．+4            B．+5             C．+6             D．+7 答案：B Her son ________ Coke, but now he ________ milk． [　　] A．used to drink ; is used to drinking B．used to drinking ; drinks C．is used to drinking ; used to drink D．is used to drink ; is drinking