$\text{Find the average of natural numbers from}\mathrm{ 1}\text{ to}\mathrm{ 69}\text{ (both included).}$

The correct option is 35.

To find the average of natural numbers from $1$ to $69$ (both included), we use the formula for the average of the first $n$ natural numbers.

The sum of the first $n$ natural numbers is given by:

$\text{Sum}=\frac{n(n+1)}{2}$

Therefore, the average of the first $n$ natural numbers is:

$\text{Average}=\frac{\text{Sum}}{n}=\frac{n+1}{2}$

Here, the number of terms $n=69$.

Substituting $n=69$ into the formula:

$\text{Average}=\frac{69+1}{2}$

$\text{Average}=\frac{70}{2}=35$

Thus, the average of natural numbers from $1$ to $69$ is 35.