According to Rowan plan of wage incentive system, bonus is paid to a worker

Answer: Option B

The Rowan plan of wage incentive system calculates the bonus based on the time saved by the worker.

According to this plan:

Option A: Whose output exceeds 67% efficiency. This is incorrect because the Rowan plan does not specifically tie bonuses to a set efficiency percentage.

Option B: On the percentage of time saved. This is correct as the Rowan plan pays a bonus based on the proportion of time saved compared to the standard time.

Option C: On the percentage of time worked. This is incorrect because the bonus is not based on the time worked but on the time saved.

Option D: On the percentage of standard time. This is incorrect because it is the time saved, not the standard time, that determines the bonus.

Therefore, the correct answer is Option B: On the percentage of time saved.