Answer:
option (D)
Step-by-step explanation:
The half life of a radio active substance is defined as he time in which the activity of radioactive substance becomes half. For example let the halflife of a radioactive substance is T, it means its activity becomes half in time T.
The relation between halflife T and decay constant K is
T = 0.6931 / K
The half life of a radioactive substance is independent to the mass of substance, temperature of substance and the addition of catalyst.
It is different for different isotopes.