In a quiz with partial answers with deduction, each selected incorrect answer cancels a correct answer in the same question. Points are harder earned this way.
Example: Let’s say we have a question with four available choices. Only two of them are correct. If a correct answer is selected followed by an incorrect answer, the correct answer will not be taken into account. This means the respondent will score only 25% on the respective question. If the form user chose the two correct choices and left out the two incorrect choices, he/she would have accomplished 100%.