Final answer:
Physical characteristics studied in genetics are called traits, which make up an organism's phenotype, determined by its genotype. The correct option is C.
Step-by-step explanation:
The term that refers to physical characteristics that are studied in genetics is c) traits. These observable traits that an organism displays are known as its phenotype, which is determined by the organism's genotype and environmental factors.
The genotype refers to the genetic makeup, including all the DNA and genes, that an organism inherits from its parents. For instance, when Mendel performed his experiments on pea plants, he observed traits like seed texture and color.
Crossing true-breeding pea plants with yellow seeds with those carrying green seeds, if yellow is dominant, typically results in F₁ offspring with yellow seeds due to the dominance of the yellow seed trait.