From a graph of plant growth (cm) versus sunlight hours with a slope of 0.8 cm per hour, what does the slope represent, and what are the units?

• A. The maximum growth achieved; units are centimeters.
• B. The growth rate per hour of sunlight; units are cm per hour.
• C. The total growth over the measurement period; units are centimeters.
• D. The intercept indicating growth without light; units are centimeters.

Answer: (B)

In this graph, the slope represents the rate at which growth changes as sunlight increases. A slope of 0.8 cm per hour means that for each additional hour of sunlight, the plant grows 0.8 cm more. The units come from how slope is defined: change in growth (cm) divided by change in sunlight hours, giving cm per hour. This describes how fast growth responds to sunlight, not the total amount grown (that would be the growth value at a specific sunlight level) and not the starting size when there’s no light (which would be the intercept, in cm).