**Core Concept**
Polio, or poliomyelitis, is a highly infectious disease caused by the poliovirus, which primarily affects the nervous system. There are three main types of poliovirus: Type 1, Type 2, and Type 3. The disease can be prevented through vaccination, which has led to significant reductions in polio cases worldwide.

**Why the Correct Answer is Right**
The correct answer, C, is incorrect because vaccine-induced polio is not typically caused by Type 2 virus. The Sabin vaccine, an oral poliovirus vaccine (OPV), contains a weakened (attenuated) form of all three poliovirus types. Although Type 2 poliovirus was declared eradicated in 2015, vaccine-derived polio (VDPV) cases have been reported, primarily due to the Type 3 virus. This is because the Type 3 virus can circulate and mutate in areas with low vaccination coverage, leading to vaccine-derived polio cases.

**Why Each Wrong Option is Incorrect**
**Option A:** Sabin vaccine is indeed an attenuated, oral vaccine, which is correct. It is used to provide immunity against polio and has been instrumental in reducing polio cases worldwide.

**Option B:** Salk vaccine, also known as inactivated poliovirus vaccine (IPV), is a killed, formalized vaccine used to prevent polio. This statement is accurate and is used in many countries, especially in areas with high polio transmission.

**Option D:** Type 1 poliovirus is indeed the most common type of virus in epidemics, which is correct. Type 1 virus is responsible for the majority of polio cases and is still prevalent in many parts of the world.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the global polio vaccination efforts have led to a significant decline in polio cases. However, vaccine-derived polio cases can still occur, particularly in areas with low vaccination coverage. This emphasizes the importance of maintaining high vaccination rates to prevent the resurgence of polio.

**✓ Correct Answer: C. Vaccine induced polio is usually due to Type 2 virus**