Final answer:
The student's claim is sentence A), while sentence B) represents a counterclaim and sentence C) represents a rebuttal.
Step-by-step explanation:
The student's claim is represented by sentence A) Students should be monitored when taking online tests. This sentence expresses the writer's stance on the topic.
Sentence B) Some say that test monitoring is an invasion of student privacy represents a counterclaim, as it presents an opposing view to the writer's claim.
Sentence C) Statistics show that more than 30% of students have admitted to cheating online, proving the need for supervision represents a rebuttal, as it provides evidence to counter the counterclaim.