I have no idea ______ it is that makes him puzzled.
What seems to be a simple idea always turns out _____ that is hard to put into practice.
I’m going to buy my daughter another interesting novel, _______ she would like to read.
(2014届湖南省怀化市高三第一次模拟考试英语试卷) We used to mistake that heavy objects fell faster than light .
The young couple have been looking for houses,but haven’t yet found _________they can afford.
Upon arriving home from a business trip, dad asked mum about my academic performance at high school and then _____ of my little sister, who was in junior school.