Fill in the blank with the correct adverb:

____ have I heard such words of wisdom from so young a speaker.

seldom

The correct answer is Option (3) → seldom

The best adverb to fill the blank is  **seldom**.

Here's why:

* **Seldom** means rarely or not often. The sentence expresses the idea that it's unusual to hear such wisdom from someone young.
**Often** and **soon** wouldn't make sense in this context.
* **Unconditionally** means without any conditions, which doesn't fit the context of hearing wise words.