Assertion (A): Activity 57 is critical.
Reason (R): Earliest finish time and latest finish time for events 57 are same
A. A is correct but R is not correct
B. R is correct but A is not correct
C. Both A and R is correct
D. Both A and R is incorrect
Answer: Option A

Critical Activity: In project scheduling, a critical activity is an activity that has no slack time. Slack time is the amount of time an activity can be delayed without delaying the entire project. If the earliest finish time and the latest finish time of an activity are the same, it means there is no slack time for that activity, making it critical.
Therefore, both Assertion (A) and Reason (R) are correct, and Reason (R) is the correct explanation for Assertion (A).