下列是初中化学常见的四个实验，请回答下列问题．
A. I'd like some carrots and fish.
B. I'd like some juice and chicken.
C. I'd like some rice and vegetables.
D. I'd like some beef and bread.
下列说法中正确的是( )
1949年3月，中共七届二中全会提出全党工作重心的转变，这意味着
