The number of carbon atoms present in a signature, if a signature written by carbon pencil weighs $1.2\times {10}^{-3}$ g is:

The correct option is B

Atomic weight of Carbon = 12 g

12 g of carbon contain $6.023\times {10}^{23}$ number of atoms.

No. of carbon atoms present in $1.2\times {10}^{-3}$ g of carbon = $\frac{1.2\times {10}^{-3}}{12}$ $\times 6.023\times {10}^{23}$ = $\times 6.023\times {10}^{19}$