题目

When _____ the prices of these goods, we must take everything into consideration. A. compared              B. comparing                C. to compare           D. compare 答案：B已知有一根长为20的铁丝，折成一个矩形框，则这个矩形框相邻两边a、b之间的函数图象大致是（ ）A．B．C．D．