Which of the following are agranulocytes?

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.

Uterine contractions during childbirth illustrate a positive feedback mechanism.

A positive feedback mechanism is a process in which the end products of an action cause more of that action to occur in a feedback loop.
This amplifies the original action.
For example, when a woman goes into labor, the pressure of the baby’s head on the cervix stimulates nerve impulses that travel to the brain and trigger the release of oxytocin, a hormone that causes the uterus to contract.
The contractions increase the pressure on the cervix, which stimulates more nerve impulses, more oxytocin, and more contractions.
This cycle continues until the baby is delivered.
Choice A is wrong because body temperature control is an example of a negative feedback mechanism, which is when the end results of an action inhibit that action from continuing to occur.
For example, when the body temperature rises above normal, the skin sweats, and blood vessels dilate to release heat.
This lowers the body temperature back to normal and stops sweating and dilation.

Choice B is wrong because control of blood sugar is also an example of a negative feedback mechanism.
For example, when the blood sugar level rises after a meal, the pancreas secretes insulin, a hormone that helps cells take up glucose from the blood.
This lowers the blood sugar level back to normal and stops the insulin secretion.
Choice D is wrong because maintaining blood pressure is another example of a negative feedback mechanism.
For example, when the blood pressure drops due to blood loss or dehydration, the heart beats faster and stronger, and the blood vessels constrict to increase the blood pressure.
This restores the blood pressure back to normal and stops the heart rate and vessel constriction.