Explanation:

- The phrase "began dropping steeply all of a sudden" suggests a rapid and sharp decline.

- Option 1: Precipitously

- Means very steeply or suddenly.

- Matches well with "dropping steeply all of a sudden."

- Correct Answer

- Option 2: Instantaneously

- Refers to something happening in an instant or immediately.

- Doesn't fully capture the idea of a steep decline over a short period.

- Option 3: Cataclysmically

- Means involving or causing sudden and violent change.

- Implies a more catastrophic, large-scale event rather than just steep decline.

- Option 4: Dramatically

- Refers to a striking or sudden change.

- Is close but doesn't specifically imply a steep or sharp drop as clearly as "precipitously."