Answer:
The answer is option (D) just noticeable difference.
Step-by-step explanation:
Just noticeable difference (JND) is a term which describes the minimum difference or amount of difference that can be sensed, detectable or noticeable.
Although Jason's razors were made thinner and finer than used to be, they didn't grab the attention of users because the changes made on the razor were below the minimum difference or amount of difference that could be noticeable by users of the razors.