One large tree supports 25000 insects. The insects are eaten by 400 small birds, and the birds are…

Step 1. (a) The numbers from the bottom are $1$, $25000$, $400$, $8$. The base is the narrowest, the second bar is the widest, and the top is narrow. The pyramid of number is not upright. It is inverted at the base.

Step 2. (b) The masses are $90000$, $2500$, $400$, $40\ \text{g}$. They fall at each step, so the pyramid of biomass is upright.

Step 3. (c) It is always upright, because the energy falls at each step.

Step 4. (d) The bird feeds at two trophic levels. A pyramid does not take into account a species that belongs to more than one trophic level.