Answer :
Answer:
**A) Obey the Pauli exclusion principle.**
Fermions are particles that follow the Pauli exclusion principle, which states that no two identical fermions can occupy the same quantum state simultaneously. This principle is a consequence of the fact that fermions obey Fermi-Dirac statistics and have half-integer spin (e.g., \( \frac{1}{2} \), \( \frac{3}{2} \), etc.).
Here's a brief overview of why the other options are not correct:
- **B) Mediate fundamental forces:** This describes bosons, not fermions. Bosons, such as photons, gluons, and W/Z bosons, mediate fundamental forces in nature.
- **C) Have integer spin:** This describes bosons. Fermions have half-integer spin, while bosons have integer spin.
- **D) Always travel at the speed of light:** Fermions, like all massive particles, do not travel at the speed of light. Only massless particles, such as photons, travel at the speed of light. Fermions have mass and therefore travel at speeds less than the speed of light.
Explanation:
