Which of the following is a producer?
a. a crow that consumes a dead animal on the side of a road
b. a fish that eats smaller fish for its food
c. a giraffe that eats the leaves of trees
d. a plant that has insect larvae feeding on its roots

D - a plant that has insect larvae feeding on its roots
A producer is basically something that makes its own food. There are some bacteria that are also producers that use chemosynthesis to produce food from inorganic substances, but most of the time it is simply plants that photosynthesise, hence the plant is the producer in this question.