Directions: For the Assertion (A) and Reason (R) given below, choose the correct alternative. Assertion (A): Vaccines prevent diseases. Reason (R): Vaccines must be given to children.

Introduction / Context:
This item tests basic biology and health awareness regarding vaccination. It also checks if students can distinguish between a scientific explanation and a recommendation. Vaccines are one of the most important tools in preventive medicine, and many public health messages emphasise childhood vaccination.

Given Data / Assumptions:

• Assertion (A): Vaccines prevent diseases.
• Reason (R): Vaccines must be given to children.
• We assume standard school biology content about immunity and vaccination.
• We must decide the truth of A and R and whether R explains A.

Concept / Approach:
In assertion–reason questions, a statement about cause or mechanism should properly explain the central idea in the assertion. Here the assertion talks about what vaccines do. The reason talks about what we should do with vaccines for children. We must ask whether “must be given to children” is a causal explanation for “prevent diseases”, or simply an important recommendation that follows from the benefit of vaccines.

Step-by-Step Solution:
Step 1: Evaluate Assertion (A). Vaccines work by exposing the body to a weakened or inactivated form of a pathogen or its components, which trains the immune system to recognise and fight the real infection in the future. In this way, vaccines help prevent specific infectious diseases. So A is true.Step 2: Evaluate Reason (R). Public health programmes all over the world emphasise that children should receive vaccines according to a recommended schedule. The phrase “must be given” expresses a strong recommendation for protecting child health and preventing outbreaks. As a general health guideline, R is considered true.Step 3: Check whether R explains A. The statement in R does not explain how or why vaccines prevent diseases. It does not describe immune memory, antibodies or any biological mechanism. Instead, it says what we ought to do with vaccines for children because they are beneficial. It is a recommendation, not a scientific explanation of the preventive effect.Step 4: Therefore, although both statements are correct, R is not the logical explanation of A in the sense required by assertion–reason questions.

Verification / Alternative check:
If R were a correct explanation of A, it should answer the question “How do vaccines prevent diseases?” or “Why do vaccines prevent diseases?”. A suitable reason would be something like “Vaccines stimulate the immune system to develop immunity against specific pathogens.” Simply saying they must be given to children describes policy or practice, not the underlying cause. This confirms that the link is not explanatory.

Why Other Options Are Wrong:
Option a incorrectly claims that R is the correct explanation of A. Option c and option d require one of the two statements to be false, which goes against established biological knowledge and standard health guidelines that recognise both the preventive role of vaccines and the importance of childhood immunisation.

Common Pitfalls:
Students often confuse “related statement” with “explanatory statement”. Because vaccines are commonly given to children, it feels natural to see R as linked to A. However, in assertion–reason questions, only a statement that describes the mechanism or cause counts as a proper explanation. It is important to read the words carefully and see whether they truly answer “why” or “how”.

Final Answer:
Both the assertion and the reason are true, but Reason (R) is NOT the correct explanation of Assertion (A).