From Statement (1)-Suppose population in Town C was 180 in 2005, 

Population in 2000= 1802/3= 120

We have the range 2000-2005 not 2000-2010 (Insufficient)

From Statement (2) we have no input on rate of increase.(Insufficient)

Using BOTH, we have

The increase from 2000 to 2005 = 180-120 (thus an increase of 60.)(From(1))

The population of Town C increased by a greater number than the range of 60 of the years 2000-2005.(From (2))

With increase > 60, lets assume it to be 61

Then population = 180+61= 241> 240.  (Hence, Sufficient as it gives us a answer of YES)

For a 100% increase, the population in 2010 must be 120+100%of 120 =240

 Thus Option(C)

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Thank You
Devmitra Sen