The provocation had an instantaneous effect on him.

Step 1: Analyze the question The underlined word is instantaneous. We need the option closest in meaning to it.

Step 2: Explain the concept Instantaneous means happening at once, with no delay. It comes from "instant," meaning a very brief moment. Its synonyms include immediate, instant, and prompt.

Step 3: Test each option

• A. a lasting: This means something that continues for a long time. It is nearly the opposite of instantaneous, which is about speed, not duration. ❌
• B. an immediate: This means happening right away, so it matches instantaneous perfectly. ✅
• C. a terrifying: This means frightening. It says nothing about timing. ❌
• D. a momentous: This means very important or significant. It looks a little like "moment," which is a trap, but it describes importance, not speed. ❌

Step 4: Answer The sentence becomes: "The provocation had an immediate effect on him." This means he reacted at once, and that matches the original meaning.

Step 5: Exam tip Watch out for look-alike words. Momentous sounds like "moment," but it means "of great importance." Instantaneous is about time, so look for words like immediate or instant. If you are unsure, put each option into the sentence and see which one keeps the original meaning.