Number of producer depends on ecosystem we are talking about. I am taking this question as terrestrial ecosystem so for the terrestrial ecosystem the answer will be group D.
In terrestrial ecosystem number of producer is higher than the second trophic level that is primary consumer. To study this we use pyramid of number. In most cases the pyramid of number is upright with members of successive higher trophic level being fewer than the previous one. The maximum number of individuals occurs at the producer level.