Read the passage below and choose one correct answer for each question.

Acupuncture

Acupuncture involves the insertion of very thin needles through the patient's skin at specific points on the body, and the needles are inserted to various depths. The medical community is not in conclusive agreement about how acupuncture works scientifically. However, we know that it does have some therapeutic benefits, including pain relief. According to WHO, acupuncture is effective for treating 28 conditions, while evidence indicates it may have an effective therapeutic value for many more. People with tension, headaches or migraines may find acupuncture to be very effective in alleviating their symptoms. Another study found that twice weekly acupuncture treatments relieve debilitating symptoms of zerostomia - severe dry mouth - among patients treated with head and neck cancer. Traditional Chinese medicine explains that health is the result of a harmonious balance of the complementary extremes of yin and yang of the life force known as chi or qi. Qi is said to flow through pathways in the human body. Through 350 acupuncture points in the body, these pathways and energy flows may be accessed.  Illness is said to be the consequence of an imbalance of the forces. If needles are inserted into these points with appropriate combinations, it is said that the energy flow can be brought back into proper balance. In Western societies and several other parts of the world, acupuncture is explained, including concepts of neuroscience. Acupuncture points are seen by Western practitioners as places where nerves, muscles and connective tissue can be stimulated.  Acupuncture practitioners say that the stimulation increases blood flow while at the same time triggering the activity of our own body's natural painkillers.

Question: In acupuncture, the insertion of the very thin needles involles with________.