Heat energy in the plants is measured in what units?
A) Grams
B) Pound
C) Decibel
D) Calorie

Hint: The plants are the most efficient organisms on earth which can convert the heat and light energy from the sun to chemical energy. This conversion is brought about by the process of photosynthesis. The plants produce carbohydrates. This carbohydrate on oxidation liberates energy in the form of ATP.

Complete answer:
The energy giving molecules in all the organisms is the carbohydrates. Carbohydrates on oxidation liberate large amounts of energy in the form of ATP. Carbohydrates and fat are the important nutrients which are known as energy giving food.

A) Heat is also a type of energy which is measured in terms of calorie. Calorie can be defined as the energy released by the breakdown of food in our body. Higher the calories present in the food, greater the energy it can liberate or provide. The extra calories generated are stored in the tissues as a form of fat. The calories or the kilocalories are the unit of the measure of nutritional energy.
B) Gram- Gram is the CGS unit used for measuring mass. The mass is defined as the amount of matter present in the object. Every living and non-living body has mass.
C) Pound- It is also the unit used for measuring weight. It is written as lb.
D) Decibel- It is the unit of sound. The human ear has a threshold range of 0-130dB. Sounds above 90dB are damaging to the ear.

Thus, the correct answer is option ‘D’.

Note: Different food items have different energy levels which are expressed in Kilocalorie per gram. Fats have the highest calorie of around 9 Kcal in one gram of food. Carbohydrates and proteins have around 4 Kcal per gram of food.