For 20 g hydrogen, the number of atoms present is 20.

The correct option is B

False

Given mass of hydrogen = 20 g
Gram atomic mass of hydrogen = 1 g
Number of atoms present in 1 mole of hydrogen = Avogadro number
= $6.022\times {10}^{23}$
Moles of hydrogen = $\frac{\text{Given mass of hydrogen}}{\text{Atomic mass of hydrogen}}$
= $\frac{20}{1}$ = 20
Number of atoms present
= Number of moles $\times$ Avogadro number
= $20\times 6.022\times {10}^{23}$ = $120.44\times {10}^{23}\ne 20$
Hence, the given statement is false.