What made my father satisfied was　　　over 50% of the students in his class had been admitted to key universities. 

Part of the reason Charles Dickens loved his own novel, David Copperfield, was ________ it was rather closely modeled on his own life.(2010·北京)

The skin is an essential part of your body and is ____ you feel cold, heat or pain.

Xiao Ming practises his spoken English once there is a chance and that is_________ it takes to live his dream to be a good guide．

(2013·安徽，21)From space, the earth looks blue.This is ________about seventy­one percent of its surface is covered by water.