In a $\text{P}$ type silicon sample, the hole concentration is $2.25 \times 10^{15} / \mathrm{cm}^{3}$. If the intrinsic carrier concentration is $1.5 \times 10^{10} / \mathrm{cm}^{3}$, the electron concentration is
- zero
- $10^{10} / \mathrm{cm}^{3}$
- $10^{5} / \mathrm{cm}^{3}$
- $1.5 \times 10^{25} / \mathrm{cm}^{3}$.