To make a multiple-choice question more challenging, what should be increased?

Increasing the plausible correctness of the distracters makes a multiple-choice question more challenging because it raises the level of difficulty in choosing the correct answer. When the distracters—incorrect options—are designed to closely resemble the correct answer in terms of relevance and factual basis, respondents must apply a deeper understanding of the material to distinguish the correct choice from the misleading alternatives.

This requires critical thinking, as well as a well-rounded knowledge of the subject matter. If the distracters are too obviously incorrect or irrelevant, it simplifies the decision-making process, making it easier for individuals to select the right answer without careful consideration. By making distracters more plausible, the question effectively tests the depth of a respondent's knowledge rather than just their ability to remember facts.

Focusing on options such as the length of answer options, the visual complexity, or the number of choices might have some effect on difficulty; however, they do not inherently enhance the critical thinking required to select the correct answer as effectively as improving the quality of the distracters does.