The indicator of presence/absence of a word in search is used in the mode . . . . . . . .

Answer: Option B

This question is about how MySQL handles searching for words within data. Let's break it down:

What is the indicator of presence/absence of a word in search?
This means we're looking for a way to know if a specific word exists in the data we're searching. Think of it like a simple yes/no answer – is the word there or not?

The answer is Option B: Boolean mode.

Here's why:
* Boolean mode works with keywords like "AND", "OR", and "NOT". It tells MySQL to look for specific words and return results based on their presence or absence.

* Natural Language mode is more complex, trying to understand the natural language of your search query. It's not focused on the simple presence or absence of words.

* Query expansion helps you find more relevant results by adding related words to your search. It's not about determining presence or absence.

* Cross mode isn't a standard MySQL search mode.

In short, Boolean mode is the most straightforward way to find out if a specific word exists in your search results.