An unknown nucleus has a nuclear density of 2.29 10 17 kg/m 3 and mass of 19.926 10 -27 kg . Its mass number A is approximately: (Take R 0 = 1.2 10 -15 m , 4 = 12.56 )

1. A. 16
2. B. 20
3. C. 12
4. D. 19

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