A professor distributes index cards to each student in his class and asks the students to write down what they think was the most important topic studied so far in the course, what is their favorite color, and what is their favorite type of music. The students do not write their names on the index cards. The professor collects the cards and reads the answers on each card to the class. This survey is considered to be

$$ anonymous.

confidential.

both anonymous and confidential.

$$ neither anonymous nor confidential.