The is a method in which neither the research participants nor the researchers know whether the participants are getting the treatment or a placebo.

What are some challenges caused by a natural monopoly? check all that apply. a. it can raise prices without concern for customers b. it is unable to serve all of the customers in market c. it lacks incentive to improve its goods and service d. it might not increase production if it cannot make a profit e. it cannot be controlled by the government or other outside forces i hope everyone has a nice day and