A barometer is used to measure air pressure!
The correct answer is 1 and 4.
Burning of fossil fuels releases harmful gases to the atmosphere which leads to climate change. Burning of hydrogen gas releases water which has no negative effect on climate.
Burning of both fossil fuels and hydrogen takes place inside expensive fuel cells.
Fossil fuels are widely available and easy to locate whereas hydrogen is available in the combined form with other elements. Hydrogen are not found in pure form on earth.
Fossil fuels are non-renewable source of energy which means they cannot be replaced in short time.
The extrapolated temperature is used to define the maximum temperature of the mixture relatively than the highest recorded temperature in which the conclusion will effect in a higher specific heat value. Heat is bound to escape from whatever apparatus is using, therefore it is needed to account for the loss of the heat that does not go into increasing the temperature of the mixture.
