Address range of 200.165.160.0 to 200.165.191.255, what is the CIDR block ?

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Given the CIDR address range of 200.165.160.0 to 200.165.191.255, what is the CIDR block?

A. 200.165.160.0/17
B. 200.165.160.0/18
C. 200.165.160.0/19
D. 200.165.160.0/20
E. 200.165.160.0/21