Question

which of the following is a warning sign of quackery?
a the promised results seem too good to be true
b someone claims that a product or service is one of many methods for treating a health problem
c a product is said to help one specific ailment
d a product contains common ingredients

Explanation:

Quackery involves false or exaggerated claims about products or services. Option A is too general, option B just states it's one of many methods which isn't a strong sign of quackery, option C is a normal claim for a product. Option D, a product claiming to cure complex diseases without proper scientific basis, is a strong sign of quackery.

Answer:

D. a product claims to cure complex diseases