第9题: [单项选择]According to the periodic table, ______ still some elements undiscovered. A. there seem to be B. it seems to be C. it seems that D. here seem 参考答案:A 答案解析:本题为存在句辨析题。存在句和if作形式主语的句子有很大的区别。存在句主要表示某处存在某物,其基本句型为there be结构,这种结构可以变化为:there is going to be,there s