根据句意，用所给单词的适当形式填空。
____ He was so tired that he stopped ________(have) a good rest.
____ The girls are old enough, they can take care of ________ (they).
____ Next Thursday is my brother's _______ (twelve) birthday.
____ There are a few _________ (different) between the twins.
____ We must be __________ (care) when we cross the busy street.
____ ______ ______ (事实上) , water covers most of the earth.
____ Kangkang is ______ his mother ______ (带…参观) his school.
____ Taiwan ______ ______ (属于) the PRC.
____ After many years'hard work, her dream ______ ______ (实现) at last.
____ The boy ______ ______ (迷路) and cried on the street.

某溶液中存在大量的H^＋、Cl^－、SO₄^2－，该溶液中还可能大量存在的是

停车场原来有10辆汽车，现在只有4辆，开走了几辆？(   )