What are pathogens?

This helps prevent blood pooling and clotting in the lower extremities, which can lead to deep vein thrombosis and pulmonary embolism.
It also reduces the workload on the heart and improves blood circulation throughout the body.
Choice A is wrong because contraction of muscles does not stimulate the arteries to vasodilate, but rather causes vasoconstriction in the inactive tissues to divert blood flow to the active muscles.
Choice B is wrong because the contraction of muscles itself does not increase heart rate significantly unless it is part of an aerobic exercise that elevates the metabolic demand.
Burning calories and keeping the heart strong are benefits of regular physical activity, not occasional muscle contraction.
Choice C is wrong because contraction of the leg muscles does not stimulate baroreceptors, which are pressure-sensitive receptors located in the walls of the arteries.

Baroreceptors respond to changes in blood pressure and signal the autonomic nervous system to adjust heart rate and vascular resistance accordingly.
Contraction of the leg muscles does not affect blood pressure or heart rate directly but rather assists with venous return.

This is because the external jugular vein drains blood from the face and scalp into the subclavian vein.
Some possible explanations for the other choices are:
Choice A. Superior vena cava.
This is wrong because the superior vena cava is a large vein that collects blood from the head, neck, chest, and upper limbs and returns it to the right atrium of the heart.
It does not drain blood from the face and scalp directly.
Choice B. Subclavian vein.
This is wrong because the subclavian vein is a vein that receives blood from the external jugular vein, the internal jugular vein, and the vertebral vein and joins with the internal thoracic vein to form the brachiocephalic vein.
It does not drain blood from the face and scalp directly.

Choice D. Cephalic vein.
This is wrong because the cephalic vein is a vein that runs along the lateral side of the arm from the hand to the shoulder and empties into the axillary vein.
It does not drain blood from the face and scalp at all.
Normal ranges for blood pressure vary depending on age, gender, health status, and other factors, but a general guideline is that systolic blood pressure (the pressure when the heart contracts) should be less than 120 mmHg and diastolic blood pressure (the pressure when the heart relaxes) should be less than 80 mmHg.