To determine how many school supply kits the volunteers could put together in 30 minutes, we first calculate the rate at which they assemble the kits.
The volunteers can assemble 40 school supply kits in 8 minutes. To find the rate per minute, we calculate:
\[ \text{Rate} = \frac{40 \text{ kits}}{8 \text{ minutes}} = 5 \text{ kits per minute} \]
Next, we want to find out how many kits they can assemble in 30 minutes. We can use the rate we just calculated:
\[ \text{Kits in 30 minutes} = 5 \text{ kits per minute} \times 30 \text{ minutes} = 150 \text{ kits} \]
Thus, the volunteers could put together 150 school supply kits in 30 minutes. The answer is A 150 school supply kits.