Ram's school looks like this from the top

Use the squares to find out the length and width of the assembly ground.

From the graph, we can see that the length of the assembly ground is $5$ squares. The width of the assembly ground is $3$squares.
The scale mentioned in the map is $1$ cm square is $2.5m$ (because $2cm = 5m$).
So, applying the scales to the map, we get:
The length of the assembly ground $=5 \times 2.5 \mathrm{m} =12.5 \mathrm{m}$ , and
The width of the assembly ground $= 3 \times 2.5 \mathrm{m} = 7.5 \mathrm{m}$
Hence, the answer is length $=12.5m$, width $=7.5m$ i.e option A