Choose the appropriate word for the meaning of the underlined word

Ravi came up on the stage and started speaking impromptu.

The correct option is Unrehearsed.

Explanation:
The word impromptu is an adjective or adverb that describes something done, said, or performed without any prior preparation, planning, or rehearsal.

Let's analyze the context of the sentence: "Ravi came up on the stage and started speaking impromptu." This means Ravi spoke on the spot without preparing his speech beforehand.

Now let's look at the given options to find the closest meaning:
1. Quickly: Refers to speed or rapid movement, which does not capture the lack of preparation.
2. Unrehearsed: Means not practiced, prepared, or rehearsed beforehand. This directly matches the definition of "impromptu".
3. Incoherently: Means in a confused or disconnected manner, which does not necessarily relate to whether a speech was prepared.
4. Impressively: Refers to doing something in a way that evokes admiration, which is unrelated to preparation.

Therefore, Unrehearsed is the most appropriate word that conveys the meaning of impromptu in this context.