Question

The complicated molecules that make up living things usually contain carbon. Why is carbon so important in this molescules?

Answer 1

Answer and explanation;
Carbon is so important in the formation of complicated molecules in that;
-Carbon can form up to four  covalent bonds, and it can form reasonably strong bonds with nitrogen, oxygen, and other different types of atoms.
-Carbon also has an almost unique ability to form long chains with C−C linkages, and along the chain there can be regions of different reactivity. 
Also C−C bond is unaffected by water, and therefore, if for example a cell, can be isolated from the aqueous medium.

Answer 2

Answer;

A. Carbon can form four strong covalent bonds.

Explanation;

Carbon can form up to 4 covalent bonds, and it can form reasonably strong bonds with nitrogen, oxygen, and other heteroatoms.

Carbon also has an almost unique ability to catenate: to form long chains with

C − C linkages, and along the chain there can be regions of different reactivity (by the presence of functional groups).