题目

已知代数式 ，请写出一个它的同类项：. 答案：【1】a2b （答案不唯一）China will spend about 52 billion yuan ______ new airports and ______ old ones in the west of China in the llth Five-Year Plan period.         [     ]A. repairing ; building              B. to build ; repair         C. building ; repairing              D. to repair ; build