Explanation:

- The sentence is: "Speech pathologists are (1) ______ in communication disabilities."

- Let's look at the options:

1. Teachers – Speech pathologists aren’t mainly teachers, though they educate, this isn’t their core role.

2. Quacks – This word is negative, meaning someone pretending to be a professional without credentials, so it doesn’t fit.

3. Experts – This fits best! Speech pathologists are skilled and have expertise in communication disabilities.

4. Relatives – Not relevant at all; being a relative doesn’t describe their professional skill.

- The word “experts” fits because it means they are highly knowledgeable in the field mentioned.

- The other words (teachers, quacks, relatives) do not match the professional, specialized role of a speech pathologist.