(B) turning
The correct answer is (B) turning, as it functions as a present participle in a participial phrase modifying the subject "Midas," describing a simultaneous action.
After a subject performing an action, a participial phrase using the -ing form (present participle) describes a concurrent action — here, the act of turning things to gold happens as Midas touches them. "Turned" (past tense) and "turns" (simple present) don't fit the participial role; "to turning" is grammatically incorrect.