Final answer:
Consensus in Kelley's covariation theory compares the behavior of one individual against the group, determining if others are behaving similarly in the same circumstances. In this case, it helps to attribute student X's late arrival to personal factors if consensus (others arriving on time) is low.
Step-by-step explanation:
The aspect of Kelley's covariation theory that compares the late arrival of student X to the on-time arrival of other students is referred to as consensus. Consensus is one of the three elements used in this theory to attribute behavior either to personal causes or to the environment. When there is high consensus, it means that other people are behaving in the same way under similar circumstances. If most students arrive on time and only student X is late, the consensus would be considered low, indicating that the lateness might be attributed to student X's personal factors rather than environmental factors.