以下说法正确的是( )
A:α衰变是原子核内的变化所引起的
B:某金属产生光电效应,当照射光的颜色不变而增大光强时,光电子的最大初动能增大
C:当氢原子以n=4的状态跃迁到n=1的状态时,要吸收光子
D:715N+11H→612C+24He是α衰变方程
It' s Sunday morning. There are many people in the park, some boys are playing basketball. There are some girls under a big tree. They' re singing and dancing. What are those women doing? They are drinking tea. Look at the woman in a blue coat. Who' s she? She' s my mother. She is talking to Edward. Edward is her student. He is a good student. He studies hard . He' s good at all the subjects. And he' s friendly to all his teachers and his friends.
现从A,B向甲、乙两地运送蔬菜,A,B两个蔬菜市场各有蔬菜14吨,其中甲地需要蔬菜15吨,乙地需要蔬菜13吨,从A到甲地运费50元/吨,到乙地30元/吨;从B地到甲运费60元/吨,到乙地45元/吨.
(1)设A地到甲地运送蔬菜x吨,请完成下表:
运往甲地(单位:吨)
运往乙地(单位:吨)
A
x
B
(2)设总运费为W元,请写出W与x的函数关系式.
(3)怎样调运蔬菜才能使运费最少?
—OK.