Concept:
Population growth generally follows the compound growth formula
\[
P=P_0\left(1+\frac{r}{100}\right)^n,
\]
where
\[
P_0=\text{Initial population},
\]
\[
r=\text{Annual growth rate},
\]
\[
n=\text{Number of years}.
\]
Step 1: Analyze Statement (I).
Given:
\[
P_0=3 \text{ crore}
\]
and
\[
r=2.5\%.
\]
The period from 2020 to 2026 is
\[
n=6.
\]
Hence
\[
P=3(1.025)^6.
\]
A unique value can be computed.
Therefore Statement (I) alone is sufficient.
Step 2: Analyze Statement (II).
Given:
Population in 2026 is twice that in 2020.
However, the population in 2020 is unknown.
Hence
\[
P_{2026}=2P_{2020}
\]
cannot be numerically evaluated.
Statement (II) alone is insufficient.