Answer:
1. EFFECT
a. Modern Western medicine can have unpleasant side effects.
b. In China, acupuncture has been found to be effective for centuries.
2. SUCEED
a. Biofeedback methods have been successful in treating headache and muscle pain.
b. The vaccine has been working successfully for the last ten years.
3. PROVE
a. There is little proof that reflexology works.
b. It is difficult to prove how herbal medicine cures illnesses.