Officials at the Unites States Mint believe that the Sacagawea dollar coin will be used
more as a substitue for four quaters rather than for the dollar bill because its weight, only 8.1gms, is far less than four quaters, which weigh 5.67 gms each.
a) more as a substitue for four quaters rather than for the dollar bill because its weight, only 8.1gms, is far less than -->
more ... rather than is unidiomaticb) more as a substitute for four quaters than the dollar bill because it weighs only 8.1gms, far lighter than -->
incompleted comparison structure, for should be added after thanc) as a substitute for four quarters more than for the dollar bill because it weighs only 8.1 gms, far less than -->
correct, more here is an adverb modifying for used, and appropriate comparison structure: S + V + prep (as) + Object (a substitude) + prep (for) + obj (four quaters) + more than + prep (for) + obj (dollar bills) + ...
Notes: its a correct comparison structure mate, a more simple exp: He likes you more than herd) as a substitue for four quarters more than the dollar bill because its weight of only 8.1gms is far lighter than it is for -->
many errorse) as a substitute more for four qurters rather than for the dollar bill because its weight , only 8.1gms, is far less than it is for -->
mentioned error