Fill in the blank with the correct word from the options given below:

The professors's explanations were so _____, that the students remained confused.

ambiguous

The correct answer is Option (2) → ambiguous

Ambiguous means open to more than one interpretation; lacking clarity or definite meaning. If the explanations are ambiguous, it logically follows that the students would be confused.

Other Options: 

• Lucid: Means expressed clearly; easy to understand. This would cause the students to be clear, not confused.

• Straightforward: Means uncomplicated and easy to understand. This would also lead to clarity.

• Enlightening: Means informing, instructing, or shedding light on the subject. This would also lead to understanding, not confusion.