Concept: This question tests your knowledge of the structure and function of neurons, specifically identifying a key component called Nissl's granules.

Why (A) is correct: Nissl's granules (also known as Nissl bodies) are large granular bodies found in the cytoplasm of neurons, particularly in the cyton (cell body) and dendrites. They are composed of rough endoplasmic reticulum (RER) and free ribosomes. Their primary function is protein synthesis, which is crucial for the growth, repair, and maintenance of the neuron, as well as for producing neurotransmitters.

Why other options are wrong:

• (B) Blood and help in nutrition and excretion: Nissl's granules are not found in blood; blood has different components for nutrition and excretion.
• (C) Sarcoplasm and help in contraction: Sarcoplasm is the cytoplasm of muscle cells, and while it contains structures for contraction (like myofibrils), Nissl's granules are specific to neurons.
• (D) Cell and secrete mucous: While some cells secrete mucous, Nissl's granules are not involved in mucous secretion and are specific to neurons, not just any cell.

Common Mistake: Students might confuse Nissl's granules with other cellular organelles or their functions, especially if they don't recall their specific location and composition.

NEET Tip / Mnemonic: Remember "Neurons Need Nissl's for New Proteins" (Nissl's, Neurons, New Proteins).

Correct Answer: (A)