Instructions
In each of the following sentences four words or phrases have been underlined. One underlined part in each sentenceis not acceptable in standard English. Pick up that part and mark its number.
Solution
Bad is the wrong word here because the sentence is describing the degree or extent of the tearing; how torn the cover is, not a moral or quality judgment.
The correct word is badly, an adverb, because it modifies the verb "torn", telling us how it is torn.
So the correct sentence is: "The book must be old, for its cover is torn badly"
