Final answer:
At high humidity and a temperature of 90°F, survival was diminished at even 20 minutes into incubation, as indicated by the significant decrease in survival rates at a 20 second exposure in the provided data.
Step-by-step explanation:
The student's question asks about the point during incubation at high humidity and a temperature of 90°F when survival is diminished. Referring to the provided data, we can determine that survival rates begin to diminish significantly at even 20 minutes into incubation. This is based on the data from a table, which indicates that the values for survival rates decrease as exposure time increases. Notably, at a 20 second exposure, the values already show a decline from the 10 second exposure, suggesting that 20 minutes into the incubation would be a critical point for diminished survival.