Select the word that is opposite in meaning to the word given below.
Soporific

Let's explore the meaning of the marked word and the given word. 
Soporific: a drug or other agent that induces sleep.​ 
Example: His voice had an almost soporific effect. 
Stimulant: a drug or substance that makes you feel more active and full of energy.
Example: Doctor Baker came and gave me a stimulant. 
From above, we can see that the correct answer is option 3. 
Additional Information:
Tranquilizer: a medicinal drug taken to reduce tension or anxiety. 
Example: For the patient showing extreme distress, a tranquilizer may be indicated. 
Hypnotic: a sleep-inducing drug.
Example: His voice had a smooth hypnotic effect. 
​Opiate: a drug derived from or related to opium.
Example: Alcohol is much less potent than opiates, however, because it works in an entirely different way.