Correct Answer: A

Rationale: The correct answer is the trachea. The trachea, commonly referred to as the 'windpipe,' is a vital structure in the respiratory system that connects the larynx to the bronchi. It is made up of cartilage rings that provide structural support, preventing collapse and ensuring the unobstructed flow of air into the lungs. The trachea plays a crucial role in facilitating the passage of air from the upper respiratory tract to the lower respiratory tract. The larynx is responsible for sound production and is located above the trachea. The bronchi are the two main branches that lead from the trachea into the lungs, further branching into smaller airways. Alveoli are the tiny air sacs where gas exchange occurs in the lungs, but they are not the structure that serves as the 'windpipe' for air passage in the respiratory system.

Correct Answer: D

Rationale: The correct answer is D, Cardiac muscle. The cardiac muscle is specifically designed to pump blood throughout the body and is found in the heart. In contrast, the bicep, tricep, and deltoid are skeletal muscles responsible for joint movement, not for pumping blood. The bicep is responsible for elbow flexion, the tricep for elbow extension, and the deltoid for shoulder abduction.

Correct Answer: A

Rationale: The correct answer is the trachea. The trachea, commonly referred to as the 'windpipe,' is a vital structure in the respiratory system that connects the larynx to the bronchi. It is made up of cartilage rings that provide structural support, preventing collapse and ensuring the unobstructed flow of air into the lungs. The trachea plays a crucial role in facilitating the passage of air from the upper respiratory tract to the lower respiratory tract. The larynx is responsible for sound production and is located above the trachea. The bronchi are the two main branches that lead from the trachea into the lungs, further branching into smaller airways. Alveoli are the tiny air sacs where gas exchange occurs in the lungs, but they are not the structure that serves as the 'windpipe' for air passage in the respiratory system.

Correct Answer: A

Rationale: The correct answer is A: Myelin sheath. The myelin sheath is a fatty layer that surrounds and insulates some nerve fibers, facilitating the rapid transmission of signals along the nerve fibers. Choices B, C, and D (Dura mater, Pia mater, and Arachnoid mater) are layers of the meninges, protective membranes that surround the brain and spinal cord. The primary function of the meninges is to protect and support the central nervous system, not to insulate nerve fibers for signal transmission.

Correct Answer: C

Rationale: Inertia is an object's resistance to a change in its state of motion, as described by Newton's first law. This means that an object will maintain its current state, whether it is stationary or moving at a constant velocity, unless it experiences an external force. Choices A and B illustrate specific instances of inertia where objects in motion or at rest continue as such without external interference. Option D refers to the force necessary to elevate an object, which is not directly linked to the concept of inertia.