半衰期和衰变常数(λ)的关系是

A、λ=0.693·T_{1\/2 <\/sub>
B、T1\/2<\/sub>=0.693·λ
C、λ·T1\/2<\/sub>=0.693
D、T1\/2<\/sub>-λ=0.693
E、T1\/2<\/sub>+λ=0.693}