The half-life period of a radioactive substance is best determined by counting the number of alpha particles emitted per second in a Geiger Muller counter from its known quantity. If the half-life period of a radioactive substance is one month, then

• A. it will completely disintegrate in two months
• B. l/8th of it will remain intact at the end of four months
• C. 3/4th of it will disintegrate in two months
• D. it will completely disintegrate in four months