Step-by-step Solution:

The time complexity of an algorithm measures its efficiency by focusing on the number of key operations performed relative to input size, not by actual runtime or hardware constraints. \[\] (a) Counting microseconds: Not used because execution time can depend on hardware. \[\] - (b) Counting the number of key operations: Correct. This represents time complexity and evaluates efficiency. \[\] - (c) Counting the number of statements: Not a precise measure of computational complexity. \[\] - (d) Counting the kilobytes of algorithm: Memory usage is not directly related to time complexity. \[\] \[\] Correct Answer The time factor is measured by: counting the number of key operations \[\] Correct Answer: (b)