The annual fluctuation in carbon dioxide concentration can best be explained by the

answer; ///(b) it is composed of four protein chains and four heme groups;

c should be the answer

igneous rocks are formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.  

the composition depends on the source magma. there are almost a thousand types of composition found till now.  

hope this