Step 1: Professional Characteristics.
Professions are distinguished by specific traits, which include:
Step 2: Option Analysis.
- (A) Specialized knowledge base: Professions possess a distinct and documented body of knowledge practitioners must master.
- (B) Theoretical underpinnings: A profession's foundation lies in theoretical knowledge, typically derived from academic pursuits, research, and specialized training.
- (C) Qualification-based entry: Access to most professions is contingent upon meeting specific educational requirements, passing examinations, or obtaining certifications to verify competency.
- (D) Service-oriented motivation: Professionals are primarily motivated by public service rather than solely by financial gain.
Step 3: Determination.
As all four attributes are fundamental to a profession, the correct selection is option 3, encompassing (A), (B), (C), and (D).
Final Answer: \[\boxed{\text{The correct answer is (3) (A), (B), (C) and (D) only.}}\]