Final answer:
The correct answer is C. 20 shifts.
Step-by-step explanation:
The correct answer to the question is C. 20 shifts.
The question states that working a certain number of shifts in a one-year period will disqualify an employee from signing up for the extra board for a month. We need to determine how many shifts will result in this disqualification.
To calculate the number of shifts that will disqualify the employee, we can set up a proportion using the given information:
10 shifts / 1 year = x shifts / 1 month
Cross-multiplying, we find that x = 10 months.
Therefore, the employee will be disqualified from signing up for the extra board for a period of one month if they work 20 shifts in a one-year period.