難度:★    考點(diǎn):介詞的使用
	
	  1.-Thanks ______ joining the Talk Show!
	
	  -You're welcome.
	
	  A. by             B. on             C. of  D. for
	
	  2.Sam likes trekking_______the jungle, because he thinks it's exciting.
	
	  A.over   B.under   C.across    D.through
	
	  3. The 30th Olympic Games will be held in London ______ about six weeks this year.
	
	  A. at   B. on    C. after   D. in
        
