Answer:
With millions of different kinds of organisms in the world, scientists must find order in all of this diversity. Scientists group living organisms into one or more of a few major categories as part discipline known as taxonomy. The bodies of organisms are organized into functional systems—cells are organized into tissues, and tissues are organized into organs. Body systems carry out critical functions, such as locomotion, reproduction, digestion, and circulation. All living things on Earth are composed of the same carbon-based, molecular building blocks.

H20+Sunlight+CO2=C6H12O6
^ ^ ^
Water Carbon Dioxide Glucose
This is called a chemical bond.
Answer is Nitrogen, atomic number 7
The atomic number of nitrogen is 7. Hence, the number of electrons in the nitrogen atom is 7. In the nitrogen, valance electrons are 3 in number in 2P orbital. Its valency is 3. Therefore, it can make three bonds with other elements which is highest among the given options.