The correct answers are: No sooner had the helicopter landed than the villain deployed the laser-equipped sharks. Hardly had the agent deactivated the bomb when the facility's alarm started blaring. Not until the smoke finally cleared did we realize the priceless diamond was missing.

Explanation of Correct Answers:

• No sooner pairs with than and requires inversion (had the helicopter landed).

• Hardly pairs with when and requires inversion (had the agent deactivated).

• With Not until, the inversion happens in the main clause, not the "until" clause (did we realize).

Explanation of Incorrect Answers:

• Scarcely... than is incorrect. Scarcely must be paired with when or before, not than.

• Only later we discovered... is incorrect because it lacks inversion. When Only + time expression starts a sentence, the main clause must be inverted: "Only later did we discover..."