Final answer:
Rocks and pebbles are the correct options that serve as abiotic factors since they are nonliving elements of the environment, unlike plants and animals, which are considered biotic factors.
Step-by-step explanation:
The student's question pertains to identifying abiotic factors from a given list. In ecology, abiotic factors are the nonliving elements of the environment that can have an impact on living organisms within an ecosystem. These factors include physical and chemical elements such as sunlight, temperature, water, and minerals. The listed options to choose from are a) Rocks, b) Plants, c) Animals, d) Pebbles. Since plants and animals are biotic factors, they are excluded from being abiotic. This leaves us with rocks and pebbles, which are inanimate objects and don't hold the properties of life.
Therefore, the correct options that serve as abiotic factors in the environment are: