---What do you know about the world's population ?

---I know that China and India are the countries ___ more than
one billion.
A.with a population of B.with populations
C.that have populations of C.which has a population of

=========C ,,,,,,,,, 为什么?

population, 人口，不用单数，因此排除A和D
常用表达法：populations of the countries, 因此B若要正确应改为with populations of
countries是名词，因此用that引导，用which也可，即把that改成which。

这是个表语从句 只能用that