The points marked A and B respectively represent
A
Half number of decayed atoms and half-life
B
Half number of atoms initially present and half-life
C
Decay constant and half-life
D
Half number of atoms initially present and time of decay
Verified Correct Answer: B.
Physical Principles & Numerical Solution
Point A is at half the initial height on the vertical axis → half the number of atoms initially present.
Point B is the corresponding time on the horizontal axis → the half-life.
Source: Official Exam / Past Question Archive