Answer
Drosophila melanogaster and Caenorhabditis elegant are not the best for making inferences about humans and other vertebrates since these model organisms are protostomes, not deuterostomes, and differ from vertebrates in many important details. They can be used to learn some useful things about vertebrates since they are animals and are convenient for experimental work.
Work Step by Step
To get this answer, try to imagine ways in which an arthropod (Drosophila) and a nematode (Caenorhabditis) are unlike vertebrates and ways in which they are similar to vertebrates.
