Neutral substance which have size of 6 nm are
**Core Concept**
The question is testing knowledge about the size of neutral substances, specifically viruses. Neutral substances in the context of virology refer to viruses that do not have a charge, making them difficult to remove using traditional filtration methods.
**Why the Correct Answer is Right**
Viruses are indeed neutral substances that can have a size of around 6 nm (nanometers). The size of a virus can vary greatly depending on the type, but many viruses are indeed in the range of 20-400 nm in diameter. The size of 6 nm is more specific to certain types of viruses such as the hepatitis B virus (HBV). The size of viruses is crucial in determining their transmission and the effectiveness of various treatments.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the correct answer as it does not mention the size of viruses.
**Option B:** This option is incorrect as it does not specify the size of viruses.
**Option C:** This option is incorrect as it does not provide any information about the size of viruses.
**Clinical Pearl / High-Yield Fact**
A notable characteristic of viruses is their ability to cause disease in humans and animals. Viruses can be transmitted through various means, including direct contact, airborne transmission, and vectors such as mosquitoes and ticks.
**Correct Answer:** D. Viruses.