The correct option is
A Squirrel, ox and tadpole.
A. Cactus, milkweed, maple tree are plants i.e. they are producers.
B. Bacteria and fungi are the decomposers.
C. Grass is the autotroph or producer and mouse and hawk are heterotrophs.
D. Squirrel, ox, tadpole are heterotrophs as they can't prepare own food and depend upon autotrophs.
E. Mushroom and moss are autotrophs and lady bug is a heterotroph.
So, the correct answer is option D- 'Squirrel, ox and tadpole'.