Option 1 -> Incorrectly matches "Gift of the gab" with the prevailing trend instead of speaking ability.
Option 2 -> Correctly matches all idioms: Gift of the gab with fluent speaking (IV), Order of the day with prevailing trend (II), In good books with being in favor (I), and Tooth and nail with fighting fiercely (III).
Option 3 -> Wrongly pairs "Gift of the gab" with being in favor and "In good books" with speaking ability.
Option 4 -> Incorrectly matches "Gift of the gab" with fighting fiercely and confuses other pairings.
Hence, Option 2: (A) - (IV), (B) - (II), (C) - (I), (D) - (III) -> "Gift of the gab" refers to eloquent speech, "Order of the day" means current necessity, "In good books" means being favored, and "Tooth and nail" means fighting with full determination -> correct