An iq test which adjusts the difficulty of future questions based on the success of earlier questions is known as a. difficulty testing. b. mental age testing. c. adaptive testing. d. group testing.
the answer is adaptive testing- the iq test will give you difficulty answers the more you get right. it adapts to you.

An IQ test which adjusts the difficulty of future questions based on the success of earlier questions is known as C. adaptive testing. 

This form of IQ testing is based on the assumption that average humans will adapt to every problem around them, so a similar problem will get easier if we do it over and over again. So as the test progress, difficulity will be reduced. So, we need to measure the result between beginning and end of the test to measure the true potential of our brain