Studies on the effectiveness of psychotherapy have found that

a. cognitive-behavioral psychotherapy is the most effective treatment for every problem
b. all psychotherapies can be used to treat any problem
c. gestalt psychotherapy is the most effective treatment for any problem
d. no one psychotherapy worked for every type of problem

Studies on the effectiveness of psychotherapy have found that

D. no one psychotherapy worked for every type of problem

Explanation:

Psychotherapy:

It is such a way of treatment that is mostly used for the patients of mental illness and psychiatric disorders. This treatment is known as talkative treatment as we talk about the patients problems rather focusing on medication.

The option A is not correct as cognitive-behavioral psychotherapy is the most effective treatment for every problem as some situation need different treatments and medication.The option B is not correct as All psychotherapies can't be used to treat any problem as some problems (disease) aren't solved by a single solution (treatment). The option C is not correct as Gestalt psychotherapy is most important in specific conditions as it tends the patients to focus on the behavior and responsibility in the present situations.