一般来说，新产品研制周期（）产品寿命周期为合理结构。
A.≤1/2
B.＞1/2
C.≤1/4
D.＞1/4
参考答案：A
— Remember to pick up your little sister on your way home.
— _____. You can depend on me. [ ]
A. Don't mention it
B. No way
C. Got it
D. My pleasure
将一定量的木炭在盛有32g氧气的密闭容器中燃烧（氧气完全反应），将生成的气体通入足量的澄清石灰水中，生成50g沉淀。生成气体中碳元素的质量分数为[ ]
A．12%
B．24%
C．36%
D．50%
