you have a typo in your question
One benefit to scientific use of SI units (or International System of Units) is that they are universal - which means that the same type of units is used everywhere in the world. America is one of the rare countries that doesn't use it, which may impede understanding.
Bacteria
Nitrogen fixing bacteria are those that convert atmospheric nitrogen to different nitrogenous ions and add them to the soil. These bacteria may either be free living in the soil, or they may develop a mutualistic relationship with some organisms, such as the nitrogen fixing bacteria that live in the root nodules of leguminous plants. An example of a genus of nitrogen fixing bacteria is the genus Azotobacter.
By process of elimination you can find the right answer. We know for a fact that carbon is found in all living organisms. That is why we talk about carbon based life forms. So the first statement cannot be true. You can figure out how many Valence electrons an element has by looking at the group number. The group number of carbon is 4 so the 2nd statement cannot be true. We know that carbon does bond with other elements because it is not a noble gas and therefore must be able to form compounds.
This means the answer must be they can form up to four covalent bonds
