The question is asking about the observable physical characteristics of organisms.
We can eliminate options B and C because they don't make much sense. An organelle is a structure in a cell which conducts cellular functions, and the morphology of an organism is basically the anatomy and physiology of the organism, which isn't quite what we're looking for.
Keeping this in mind, here is some information on prefixes:
geno - relating to genes
pheno - relating to what's observable
The second one sounds a lot like what we're looking for, and just in case, the definition of phenotype is the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.
Therefore your answer is: A. phenotypes