Please read the following examples from released SATS, which collectively show the types of questions pertaining to comparisons.
Remember: Use "more" and "-er" when comparing two things. Use "most" and "-est" when comparing three or more things.
Lions and tigers may be identifical in size, but the tiger is the fiercer animal and the lion the strongest. (Only two things are being compared. "Strongest" should be "Stronger.")
Just how critical an improved balance of trade is to a healthy economy has never been more clearer than it is now. (Redundant. Either say "more clear" or "clearer," but note both at the same time!)
The novel Pride and Prejudice by Jane Austen was once more widely read and was more popular in high schools in the United States than Charlotte Bronte. (This sentence compares a book to a person.)
Nearly all of the editors of the magazine agree that of the two articles to be published, Fujimura's is the more exciting. (Correct as given! Note only two articles are being compared.)
The campus newspaper does not print as much world news as does my hometown. (Incomplete comparison: Try "my hometown newspaper.")
In the United States, the industrial use of plastics is greater than steel, aluminum, and copper combined. (Incomplete comparison: Try "the combined use of steel, aluminum, and copper.")
Because they painted scenes of life as ordinary people lived it, rather than scenes from myths, many nineteenth-century American artists differed from earlier times.