Which pyramid is always upright ? Why?

Explanation

(1) The pyramid of energy is always upright.
(2). This is because, only 10% of the energy present in a tropic level transfers to the other level.
(3). If there are 1000 calories of net production at producer level, only 10 calories at first carnivore level and 1 calorie at top carnivore level.
(4) The flow of energy from producers to consumers is unidirectional.