Answer: horizontal, demand
Step-by-step explanation:
The demand curve would reveal the demand for construction workers. Also demand slopes from left to right and so to find demand quantity(demand for construction workers) the horizontal axis of the graph would be considered. This is because demand(dependent variable) is dependent on price(independent variable) which is on the vertical axis, therefore we consider the horizontal axis when we wish to find demand given a certain a price from the y axis(price, independent variable).