During transmission over a certain binary communication channel, bit errors occur independently with probability $p$. The probability of AT MOST one bit in error in a block of $n$ bits is given by

- $p^{n}$
- $1-p^{n}$
- $n p(1-p)^{n-1}+(1-p)^{n}$
- $1-(1-p)^{n}$