According to NFPA 101, Life Safety Code, an Assembly Occupancy is defined as a space used for the gathering of 50 or more persons. Since the question specifies that the conference rooms are used for meetings of less than 50 people, they do not meet the threshold for an Assembly classification. Instead, such spaces are classified based on the primary occupancy they serve. Conference rooms are a typical accessory use within an office environment, which falls under the Business Occupancy classification. Therefore, these rooms are classified as Business Occupancy.

A. Assembly: This is incorrect because the occupant load is less than the 50-person threshold required by NFPA 101 for an Assembly Occupancy classification.

C. Mercantile: This is incorrect as Mercantile Occupancies are used for the display and sale of merchandise, which is not the function of a conference room.

D. Educational: This is incorrect as Educational Occupancies are used for educational purposes through the 12th grade for groups of six or more students.

1. NFPA 101®, Life Safety Code®, 2021 Edition. Section 6.1.2.1, "Assembly occupancies include, but are not limited to, all buildings or portions of buildings used for the gathering of 50 or more persons..."

2. NFPA 101®, Life Safety Code®, 2021 Edition. Section 6.1.8.1, "Business occupancies are occupancies used for the transaction of business, other than mercantile." This section lists "Offices" as a typical example.

3. Worcester Polytechnic Institute (WPI), Fire Protection Engineering (FPE) Courseware, FPE 553: Fire Protection for Industrial and High-Hazard Occupancies. Course materials on occupancy classification consistently teach that assembly-type spaces with an occupant load under 50 are classified as part of the main occupancy (e.g., Business).

4. University of Maryland, Department of Fire Protection Engineering. ENFP 625, "Enclosure Fire Modeling." Course curriculum covers fundamental principles of the Life Safety Code, including the distinction between Assembly and Business occupancies based on the 50-person occupant load threshold.