已知⊙O1的半径为1cm，⊙O2的半径为4cm，O1O2长为3cm，则⊙O1和⊙O2的位置关系是[ ]
A．内切
B．外切
C．相交
D．内含
答案：A
The doctors and nurses arrived at the _______ soon after the accident happened, so no
people died from it.[ ]
A. grave
B. buffet
C. scene
D. passage
从经济效益的角度对新产品概念进行商业分析，包括两个具体步骤：一是（），二是推算成本与利润。
