Suppose yesterday morning you noticed ice crystals (frost) on the grass, yet the minimum temperature reported in the newspaper was only 35o F. The most likely reason for this apparent discrepancy is that:

The correct answer is: A. Temperature readings are taken in instrument shelters more than 5 feet above the ground.

The temperature reported in the newspaper is the temperature that was recorded in an instrument shelter. Instrument shelters are designed to protect the thermometer from direct sunlight and wind, which can cause the temperature to read higher or lower than the actual air temperature. The shelter is also placed at least 5 feet above the ground to avoid the effects of ground heat or cold.

If the thermometer was read before the minimum temperature was reached for that day, the temperature would be higher than the actual minimum temperature. If the thermometer was read incorrectly, the temperature would also be incorrect. However, these are less likely explanations for the discrepancy between the observed frost and the reported temperature.

The most likely explanation is that the temperature reading was taken in an instrument shelter, which is designed to protect the thermometer from direct sunlight and wind. This would explain why the temperature reported in the newspaper was higher than the actual temperature on the ground, where the frost was observed.