Heart disease is a malformation of the heart present at death

a. Global warming

Explanation:

Solar energy is the form energy which uses the SUN as Its source. It is a renewable source of energy. Humans, through our activities, contribute to the gradual increase of the earth's atmospheric temperature, called GLOBAL WARMING. We contribute to this phenomenon posing threat to the environment's sustainability when trying to fulfil our day-to-day individual needs.

One of those activities is the burning of fossil fuels via cars, in industries, domestic households etc. The burning of fossil fuels results in the release of heat-trapping gases called Greenhouse gases e.g CO2, CFC etc. These gases are the major cause of Global warming.

Hence, Joe is trying to work on how solar energy can replace the use of other sources of energy that release these greenhouse gases into the atmosphere in order to curb GLOBAL WARMING.

N.B: Solar energy does not emit greenhouse emissions. It is the best and safest source of energy.