All employee surveys are sent out by the Human Resources Department and all employee surveys are kept confidential.

Based on the information above, which of these statements MUST be true?

Nothing that is kept confidential is sent out by the Human Resources Department.

At times, materials sent out by the Human Resources Department are kept confidential.

Whenever the Human Resources Department sends out materials, they are kept confidential.

At least some of the materials sent out by the Human Resources Department are not kept confidential.

All materials that are confidential are sent out by the Human Resources Department.