Let's go step by step, explaining each answer: --- ### 1. Recombination rate of excess electrons and holes is determined by: **Selected Answer:** b. Combined lifetime of both majority and minority carriers **Explanation:** The recombination rate in a semiconductor depends on how long both majority and minority carriers exist before recombining. The combined lifetime of both types of carriers determines how quickly they recombine. --- ### 2. A reverse bias p-n junction diode has: **Selected Answers:** a. Almost no current b. High resistance **Explanation:** When a p-n junction diode is reverse biased, the current through the diode is very small (almost negligible), and the diode behaves like a high resistance device. The depletion region widens, and only a tiny leakage current flows. --- ### 3. According to SRH theory, if capture cross section of trap sites is more then: **Selected Answer:** d. Recombination rate increases **Explanation:** Shockley-Read-Hall (SRH) theory states that the recombination rate increases if trap sites have a larger capture cross-section because more carriers get trapped and recombine. --- ### 4. Under the influence of constant external electric field applied, free charge carriers: **Selected Answer:** d. Reach a certain velocity and then de-accelerates **Explanation:** When a constant electric field is applied, charge carriers accelerate until they reach a certain drift velocity due to scattering with atoms (saturation velocity). If the field gets very high, they may even experience velocity saturation and then de-acceleration due to increased scattering. --- ## Final Answers: 1. **b. Combined lifetime of both majority and minority carriers** 2. **a. Almost no current, b. High resistance** 3. **d. Recombination rate increases** 4. **d. Reach a certain velocity and then de-accelerates**