To determine the temperature range at which most bacteria start to multiply rapidly, we need to properly match the temperature ranges provided with the known behavior of bacterial growth.
1. 41°F - 135°F: This temperature range is widely recognized as the "danger zone" for bacterial growth. Most bacteria can grow rapidly when the temperature is between these limits.
2. 34°F - 40°F: This is the range in which refrigeration temperatures are maintained. Most bacteria growth slows down considerably in this range, although some can still grow slowly.
3. 50°F - 70°F: While some bacteria can grow in this temperature range, it is not generally considered the primary range for rapid bacterial multiplication.
Given these insights, the range of 41°F - 135°F is the most appropriate for rapid bacterial multiplication. Hence, the correct key term number is:
1