The pyramid of numbers becomes partly inverted and partly erect for which of the following?

Inverted pyramid is found in

$A$ pyramid of number in a grassland ecosystem shows:

Consider the following statements about ecological pyramids:
$I.$ Charles Elton developed the concept of ecological pyramid.
$II.$ After his name,these pyramids are also called as Eltonian pyramids.
$III.$ It is a graphical representation or pyramid-shaped diagram which depicts the number of organisms,biomass,and energy at each trophic level.
Which of the statements given above are correct?

The pyramid of energy is always upright for any ecosystem. This situation indicates the fact that . . . . . .

Choose the correct option for the given statements:
($T$ = True,$F$ = False)
$(A)$ Pyramid of energy is always upright.
$(B)$ Pyramid of number in a sea is generally inverted.
$(C)$ Pyramid of biomass in a sea is generally inverted.
$(D)$ In most ecosystems,the pyramid of number and energy are always inverted.