Which type of test item has the greatest probability of guessing?

The type of test item that has the greatest probability of guessing is true/false items. This is primarily because there are only two possible answers to each question, meaning that a student has a 50% chance of guessing correctly. In contrast, multiple-choice items typically offer several answer choices, reducing the probability of guessing the correct one to less than 50%, depending on how many options are provided. Supply-type and fill-in-the-blank questions generally require more knowledge and do not provide any cues or options, making guessing less likely to yield a correct answer. Therefore, true/false questions stand out as having the highest likelihood of being successfully answered through sheer chance alone.