Correct answer: (D) always upright

Explanation:

In grassland ecosystem, the shape of pyramid of number is always upright. It is called as pyramid of numbers. In this, the energy is maximum at producer level, followed by primary consumer level (herbivores), followed by secondary consumer level (carnivores). The base of the pyramid of number represents the producers in a grassland ecosystem.

Thus, the correct answer is 'Always upright.'