如图所示电路，电源内阻r=1Ω，R1=2Ω，R2=5Ω，灯L标有“3V，1.5W

国内家电生产企业主要产品已进入产品生命周期的成熟期，它们选择的目标市场涵盖战略应当是（）。

A、大量市场营销

B、差异市场营销

C、集中市场营销

D、无差异市场营销

I eager to go to college because I know there is so many to learn about the world

and about human beings. Knowledge is source of pleasure for me. I want to study at a

college for fun to knowledge; I know college education can prepares me better for my

future. Better education mean, more often then not, better jobs, better opportunities and

better choices. I want to go to college because I know that our parents and other people

care for me will be happy with that. Unless I can study at a nice university, I will make

them happy. I’d like not let them down. That’s why I must go to college.

高速缝纫机在转速为5000转/分时，缝针的温度可达（）。

A、约100度

B、约200度

C、约300度

D、约500度

设S：x²+y²+z²=a²（z≥0），S₁为S在第一卦限中的部分，则有（）。

A.A

B.B

C.C

D.D

YJ29滤嘴接装机双倍长滤嘴烟支由吸风固定在切割鼓轮烟槽中，并由内、外端部导轨固定在（）。