**Core Concept**
Biological fixation of nitrogen is a process where nitrogen is converted from atmospheric nitrogen (N2) into a usable form for plants, primarily through the action of certain bacteria and cyanobacteria. This process is crucial for plant growth and development, especially in nitrogen-poor soils.

**Why the Correct Answer is Right**
Legumes, such as soybeans, beans, and peas, have nodules on their roots where Rhizobia bacteria reside and fix atmospheric nitrogen into a form that can be used by the plant. This process is made possible by the presence of enzymes like nitrogenase, which catalyzes the reduction of atmospheric nitrogen to ammonia (NH3). The nitrogen fixed by legumes is then used for plant growth and development, and some of it can be stored in the plant's tissues, making it available for subsequent crops.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to biological nitrogen fixation, as it does not involve the action of nitrogen-fixing bacteria.
**Option B:** While certain types of grasses may have nitrogen-fixing bacteria associated with them, they are not the primary crops that undergo biological nitrogen fixation.
**Option C:** Crops like corn and wheat are not capable of biological nitrogen fixation, as they do not have the necessary nodules or bacteria associated with them.

**Clinical Pearl / High-Yield Fact**
Legumes are a valuable crop for improving soil fertility, as they can fix atmospheric nitrogen and reduce the need for synthetic fertilizers. This makes them an important component of sustainable agriculture and crop rotation strategies.

**Correct Answer:** C.