题目

人类的眼色有褐眼和蓝眼之分，是由眼球      的色素决定的。（ ）A.角膜B.玻璃体C.瞳孔D.虹膜 答案：【答案】D【解析】人类的眼色由眼球虹膜的色素决定的。所以答案是：DWe find  _____impossible for us to learn a foreign languagewell in a short time. [     ]A. thatB. thisC. oneD. it