Explain rate of decay of a material?

Decay Rate

The half-life (t1/2) is the time taken for the activity of a given amount of a radioactive substance to decay to half of its initial value. The mean lifetime (τ, “tau”) is the average lifetime of a radioactive particle before decay. The decay constant (λ, “lambda”) is the inverse of the mean lifetime.

The rate of radioactive decay is an intrinsic property of each radioactive isotope that is independent of the chemical and physical form of the radioactive isotope. ... Activity is usually measured in disintegrations per second (dps) or disintegrations per minute (dpm).

The half-life (t1/2) is the time taken for the activity of a given amount of a radioactive substance to decay to half of its initial value. The mean lifetime (τ, “tau”) is the average lifetime of a radioactive particle before decay. The decay constant (λ, “lambda”) is the inverse of the mean lifetime.

the answer is a i think