Which layer of soil is best for plant growth (asap! )

The A horizon is the best for plant growth, because is has more organic material and more organisms that make the soil more fertile than the deeper layers, and the soil is not loose like the O horizon.

the A horizon

i would say the prokaryotic cells the prokaryotic cells are less complex, are usually found only in unicellular organisms and have more limited capabilities than eukaryotic cells.

substitution is the answer in this case