请根据括号内汉\英语提示或已给的首字母写出单词的正确形式。
To our surprise , he made no ____________（解释）of his absence.
Tibet is a  ____________（多山的） province .
U______________, my computer system broke down again .
The learner of a second language has many difficulties to ___________(克服)
His experiment ended in _______(失败).
He returned from Paris and found his office was under someone else’s________(占领)．
At that time, hunger was a ______ problem in many countries.（令人不安的）。
He has made a________(总结)of the main points in the professor’s speech.
He made some ________(评论)about my dress，and then carried on reading his book.
Though he is young, he is s_________ to support a large family. (努力)