Explanation: FCC regulations, specifically Part 1, Section 1.1310, and OET Bulletin 65, define Maximum Permissible Exposure (MPE) limits for radiofrequency energy. These limits specify different averaging times depending on the exposure environment. For "controlled" environments, where individuals are aware of the potential for exposure and can exercise control over it (e.g., amateur radio operators in their shacks, workers near broadcast antennas), the MPE limits are averaged over **6 minutes**. This shorter period applies to individuals who are professionally trained or knowledgeable about RF safety. In contrast, for "uncontrolled" environments, where the general public may be exposed without their knowledge or ability to control the exposure (e.g., public areas near antennas), the MPE limits are averaged over **30 minutes**. This longer averaging period provides a greater safety margin for the general population, who may not be aware of or able to mitigate RF exposure risks. Therefore, the combination of 6 minutes for controlled and 30 minutes for uncontrolled environments is correct. The other options present incorrect averaging times as defined by the FCC rules.