Final answer:
During an isometric process, reducing the temperature of a monatomic ideal gas to one-half of its original value results in the pressure of the gas decreasing to half its original value.
Step-by-step explanation:
When a monatomic ideal gas is cooled to one-half its original temperature during an isometric (constant volume) process, the final pressure of the gas decreases to half its original value according to Gay-Lussac's Law which states that the pressure of a given amount of gas held at constant volume is directly proportional to the Kelvin temperature. Thus, the correct answer to this question is B) decreases to half its original value. During an isometric process, reducing the temperature of a monatomic ideal gas to one-half of its original value results in the pressure of the gas decreasing to half its original value.