A frog population is living in the lake near the campus. After a field survey, scientists reported that there are estimated 650 frogs in the lake area (which is 130 squared meter in size).
The population density of this frog population is _____.

A. 650 frogs
B. 5 frogs per squared kilometer
C. 5 frogs per squared meter
D. 13 frogs per squared meter
E. 130 frogs