Step 1: State Cattell’s contribution.
Using factor analysis, Cattell distilled observable behaviors into 16 source traits measured by the {16 Personality Factors (16PF)} questionnaire.
Step 2: Clarify terminology.
“Source traits” are basic building blocks; many “surface traits” (visible habits) are combinations of these 16.
Step 3: Conclude.
\[
\boxed{\text{Sixteen (Option A).}}
\]