Read the passage carefully and choose the best answer to each question out of the four alternatives and click the button corresponding to it. According to this immunology passage, what exactly are antibodies that take part in the antigen–antibody reaction?

Introduction / Context:
This reading comprehension question is based on a short scientific passage about the immune system, specifically the antigen antibody reaction. Competitive examinations often test English through such factual passages, where the candidate must identify the precise meaning of words and phrases taken from the text. Here the focus is on the term antibodies and on understanding their biological nature as described by the passage, not on outside general knowledge alone.

Given Data / Assumptions:

• The passage explains the antigen antibody immunological reaction.
• It states that antibodies are proteins synthesized by specialized cells called plasma cells.
• Plasma cells are formed by lymphocytes when an antigen comes in contact with them.
• The question asks what antibodies are according to the passage.
• We assume that the correct option must closely match the wording and idea used in the passage.

Concept / Approach:
The key concept here is factual detail recognition. In reading comprehension, the safest way to answer such a question is to go back to the relevant sentence in the passage and read it carefully. The question asks what antibodies are, so we should directly locate the sentence that defines antibodies. Once we identify the definition, we compare that wording with the answer options and choose the one that preserves both the meaning and the emphasis of the original line. Options that add new ideas, distort the meaning, or contradict the passage must be rejected even if they sound scientific.

Step-by-Step Solution:
Step 1: Locate the defining sentence about antibodies in the passage. Step 2: The passage states that antibodies are proteins synthesized by specialized cells called plasma cells. Step 3: Note that this description includes two ideas: antibodies are proteins, and these proteins are synthesized by plasma cells. Step 4: Examine each option and ask which one matches this explanation most faithfully. Step 5: Option C says protein molecules synthesized by plasma cells in response to antigens, which captures both that they are proteins and that plasma cells synthesize them when antigens appear. Step 6: The other options either talk about dead cells, minerals, sugars, or fats, none of which match the passage. Step 7: Therefore, Option C is the correct answer.

Verification / Alternative check:
A quick cross check is to test whether the chosen answer fits back into the passage logically. If we replace the term antibodies in the text with protein molecules synthesized by plasma cells in response to antigens, the sentence still makes clear biological sense. If we try to replace antibodies with minerals, dead cells, sugars, or fats, the description of immunological reactions immediately sounds wrong from both the passage perspective and basic biology. This confirms that the selected option is consistent with the context and preserves scientific accuracy as described in the passage.

Why Other Options Are Wrong:
Mineral substances stored inside the body cells is incorrect because the passage does not mention minerals at all in defining antibodies, and antibodies are not minerals. Dead cells that no longer perform any function is wrong because the passage states that antibodies are synthesized proteins, not dead or inactive cells. Simple sugars that circulate in the bloodstream is incorrect because sugars serve as energy sources, not as antigen specific immune proteins. Fat molecules that provide energy during infections is also wrong, because fats are energy reserves and are not described as specific antigen binding molecules in the text.

Common Pitfalls:
A common mistake in such questions is to rely only on general knowledge or on vague impressions about immune system terms without going back to the exact wording of the passage. Another pitfall is to be misled by answer choices that sound scientific or technical but do not match the description in the given text. Students may also choose an answer that partially matches, such as simply proteins, without capturing the full nuance that they are synthesized by plasma cells in response to antigens, which is why carefully reading the complete sentence is important.

Final Answer:
The correct answer is Protein molecules synthesized by plasma cells in response to antigens.