Given $n$ independent Bernoulli random variables, taking value $1$ with probability $p$ and $0$ with probability $1-p$. Then, which of the following is the value of $E\left[\left(z_{1}+\right.\right.$ $\left.\left.\ldots z_{n}\right)^{2}\right] ?$
- $0$
- $n p+n(n-1) p^{2}$
- $n^{3} p^{2}$
- $n^{2} p^{2}+n p$
- None of the above