If there are much more people in the world, there must have more food to feed the people. But food is already a problem in today world. One-third of the world's population is starving, because there is not enough food. Ten thousand people died of hunger every day in some parts of the world. But in others parts of the world, people become ill or die, because they eat too much food, and they are very fat. Some countries have no food, but the others have too much, and they throw them away. How can tomorrow's world feed its people? The world needs produce more food than it does now.

合成腈纶的单体是：（）

A、丙烯

B、丙烯酸

C、丙烯腈

D、以上均不是