Concept: A reference librarian helps users locate information, but no librarian can answer every possible question immediately because information needs may be broad, specialized or unavailable.
Step 1: Check Assertion A.
A reference librarian may not be able to answer all questions because some questions may require specialized sources, expert knowledge or detailed research.
\[
A = \text{Correct}
\]
Step 2: Check Reason R.
The reason says reference librarians are less-intelligent people. This statement is incorrect and inappropriate. Inability to answer every question does not mean lack of intelligence.
\[
R = \text{Incorrect}
\]
Step 3: Choose the correct option.
Since A is correct but R is incorrect, the correct answer is option (C).