Answer the following question given this paragraph: 

Chapter 2 1 Figure 2.3 Carbon-12 has six neutrons. Carbon-13 has seven neutrons. 3 Figure 2.24 C 4 A 6 C 8 D 10 C 12 D 14 Ionic bonds are created between ions. The electrons are not shared between the atoms, but rather are associated more with one ion than the other. Ionic bonds are strong bonds, but are weaker than covalent bonds, meaning it takes less energy to break an ionic bond compared with a covalent one. 16 Buffers absorb the free hydrogen ions and hydroxide ions that result from chemical reactions. Because they can bond these ions, they prevent increases or decreases in pH. An example of a buffer system is the bicarbonate system in the human body. This system is able to absorb hydrogen and hydroxide ions to prevent changes in pH and keep cells functioning properly. 18 Carbon is unique and found in all living things because it can form up to four covalent bonds between atoms or molecules. These can be nonpolar or polar covalent bonds, and they allow for the formation of long chains of carbon molecules that combine to form proteins and DNA.


Q: What is unique and found in all living things because it can form up to four covalent bonds between atoms or molecules?

 Choices:

- hydrogen

- oxygen

- potassium

- carbon

A:
carbon
