heat index combines the effects of air temperature and ect one: a. cloud cover b. relative humidity c. solar intensity. d. wind speed. e. air pressure.

heat index combines the effects of air temperature b. relative humidity

Explanation:

The heat index that affects the air above is the humidity as the amount of heat energy that reaches the ground in the form of sunlight is blocked by clouds and wind speeds reduce the heating effects air pressure can range from high to low but it does not impact the air temperatures much. The heat index was developed by George Winterling in 1978 as a "humiture" which states that the heat index is a combination of temperature and humidity in this variable takes into account the shadiness and available moisture content. Thus relative humidity is a heat index that is considered when making changes in temperature in an outdoor-related environment. As heat is a factor that is affected by precipitation and evaporation and thus releases of latent heat from the body.

b. relative humidity

Explanation:

The heat index, it is the measure of how the temperature feels to human body when the relative humidity is combined along the temperature of the air.

The body feels warmer in humid condition, due to the increased humidity the sweat will not evaporate and hence wont give cooling sensation to the body.

Similarly our body feels cooler in the arid conditions because the sweat evaporate quickly cooling our body.

Thus, as the air temperature and relative humidity increases the heat index also increase.