A. According to the number marked in the lower right corner of the element symbol indicating the number of atoms contained in a molecule, it can be seen that a molecule of allicin consists of 6 carbon atoms, 10 hydrogen atoms and 3 sulfur atoms. Atomic composition; therefore A is correct;

B. According to the chemical formula of allicin is C6H10S3, it can be seen that allicin is composed of three elements: carbon, hydrogen and sulfur; therefore B is correct;

C , According to the mass ratio of each element in the compound = the relative atomic mass of each element x the number of atoms, the mass ratio of carbon, hydrogen and sulfur in allicin is: 36:5:48; therefore C is wrong; < /p>

D. The formula weight of allicin = 12×6+1×132×3, so D is correct;

So choose C.