Compound can be described using element symbol and numbers . it is a mixture which is result of two or more chemical element in such a way that atoms of different elements held together by chemical compound that are difficult to break . Most often a compound looks and behave like an element
for example :- Hydrogen and oxygen .. both of these elements are gaseous at room temperature and atmospheric pressure , but when both combined they both form compound water . ( H2O )
The correct should be A. thousands of galaxies
Following the law of conservation of mass, the mass percent of hydrogen in the resulting compound is 14.4%(wt/wt). This is assuming that all of the carbon reacts with all of the hydrogen. The solution is as follows:
mass % = mass hydrogen*100/total mass = 28.8*100/(28.8+171.2) = 14.4%