Need help with comparison!

[vv0510_vn]

The population of the US is ______. A greater than Canada
B more than the population Canada
C greater than that of Canada
D greater than Canada's one

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Which one should I choose? I think both answer C and D are correct. Could anyone please tell me what the difference between them is?
Any help would be appreciated!

[shalstudent]

Its C.

The population of the US is greater than that of Canada.

You may also say: The population of the US is greater than Canada's.

[RonBee]

Originally Posted by shalstudent

It's C.

The population of the US is greater than that of Canada.

You may also say: The population of the US is greater than Canada's.

You could also say the US is bigger than Canada (in population). Also: the US is more populous than Canada.