For private key crypto for communication between each pair of individuals on secret key will be required, so if an individual wants to communicate with other $\text{n-1}$ individuals he should have $\text{n-1}$ secret keys,
So, the total number of secret keys for private encryption,
$=n\times (n-1)$ (If we include copies) or $n\times \dfrac{(n-1)}{2}$ (distinct keys).
For public key encryption each individual needs to have a public and private key,
so the total keys required in $2\times n$.
From the tone of the question the answer seems to be C) $\dfrac{n(n-1)}{2}$ and $2n$.