A multiple-choice test has 30 questions. Each question has three choices, but only one choice is correct. Using a random number table, which of the following methods is a valid simulation of a student who circles his or her choices randomly? Explain.

a. The digits 1, 2, and 3 represent the student’s attempt on one question. All other digits are ignored. The 1 represents the correct choice, the 2 and 3 represent incorrect choices.

b. The digits 0, 1, 4 represent the student’s attempt on one question. All other digits are ignored. The 0 represents the correct choice, the 1 and 4 represent incorrect choices.

c. Each of the 10 digits represents the student’s attempt on one question. The digits 1, 2, 3 represent a correct choice; 4, 5, 6, 7, 8, 9 and 0 represent an incorrect choice.