​One-third of the sum of all the prime numbers greater than 5 but less than 18 is the square of:

​One-third of the sum of all the prime numbers greater than 5 but less than 18 

All the prime numbers greater than 5 but less than 18 = 7,11,13,17

Sum of prime numbers = 48

​One-third of the sum of all the prime numbers = $$\frac{48}{3}$$

​​One-third of the sum of all the prime numbers = 16

Number = 16

Number = $$\sqrt{16}$$

The square of number = 4

Thus, option (b) is correct.

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