【正确答案】：
A CURIOUS, MOST UNCHILDLIKE PERSISTENCE, A CONTROLLED IMPATIENCE, MADE HIM WAIT. IN THE MEANTIME, HE LAY UNDERWATER ON THE WHITE SAND, LITTERED NOW BY STONES HE HAD BROUGHT DOWN FROM THE UPPER AIR, AND STUDIED THE ENTRANCE TO THE TUNNEL. 
【题目解析】：考点：persistence：坚持不懈；impatience：急躁，不耐烦；in the meantime：同时；entrance：入口。句子结构：句子主干impatience made him wait；he lay underwater。