The number of workers have increased steadily each year means _____.
Answer Details
The correct statement is "The number of workers has increased steadily each year." This means that the amount of people working has been getting bigger every year, without any sudden jumps or decreases. The word "steadily" emphasizes that the increase has been happening consistently over time. The verb "has" is used because "number" is a singular noun, so it requires a singular verb.