Complex sentence: A Classroom Response System (CRS) is a tool used where the students each have a handheld device that syncs up with the instructor's computer, through which the instructor poses primarily multiple choice or true/false questions and the students answer on their device.
Split into simpler sentences: A Classroom Response System (CRS) is a tool used where the students each have a handheld device that partners up with the teacher's computer. The instructor then asks multiple choice or true/false questions and the students answer on their device.