[Here in the US, we spell it "meters".]

Get them all to the same units.  The first one is

  .

So we know A is bigger than D.

1 hectare is 10000 square meters, so 2 hectares is 20000 square meters,

so A is still the biggest so far.

Now we must check C.

1 acre = 4046.9 square meters.

So 3 acres is 3×4046.9 = 12140.7 square meters.

So the biggest area is A.

Edwin