The upright pyramid of numbers is absent in?

Correct Answer: D. Forests

Forests (option D) are typically characterized by a complex and diverse ecosystem with multiple trophic levels. Therefore, the upright pyramid of numbers is less likely to be absent in forests compared to the other options.
The upright pyramid of numbers is more likely to be absent in aquatic ecosystems like lakes (option A) and ponds (option B), where the primary producers, such as phytoplankton, can be very abundant, supporting a large number of herbivores and subsequently carnivores. This can lead to an inverted pyramid of numbers, where the number of organisms at higher trophic levels exceeds those at lower trophic levels. Therefore, the correct answer is: D. Forests