How many growing degree days are there if the maximum temperature was 85 and the minimum was 55?

To calculate growing degree days (GDD), the formula used is:

GDD = (maximum temperature + minimum temperature) / 2 - base temperature.

Typically, the base temperature is set at 50°F for many crops, particularly in agronomy contexts.

Using the given maximum temperature of 85°F and minimum temperature of 55°F:

1. First, add the maximum and minimum temperatures:

85 + 55 = 140.

2. Then, divide by 2:

140 / 2 = 70.

3. Next, subtract the base temperature (50°F):

70 - 50 = 20 GDD.

This indicates that the calculated growing degree days is 20. The correct answer is based on the understanding that GDD provides insight into crop development stages by assessing temperature accumulation. Thus, acknowledging the growing degree days helps with effective agricultural planning and forecasting. The other options do not align with this calculation methodology, as they do not yield the correct number based on the formula applied.