Read the sentence carefully and select the synonym of the underlined word from the given alternatives.
The Television show was hosted by a young and vivacious woman called Laura.

The correct answer is Energetic.

Explanation:
In the given sentence, the word vivacious means attractively lively and animated, full of high energy and enthusiasm.

Let's analyze the given options to find the correct synonym:

1. Energetic: Possessing or demonstrating great activity, vitality, or energy. This matches the meaning of "vivacious" closely.
2. Liberal: Open to new behavior or opinions; generous or lenient.
3. Legendary: Remarkable, famous, or described in well-known stories.
4. Atrocious: Extremely wicked, cruel, or of very poor quality.

Therefore, the word Energetic is the accurate synonym for vivacious.