A radioactive nucleus can decay by two different processes. The half-life for the first process is \[{{t}_{1}}\] and that for the second process is \[{{t}_{2}}\]. If effective half-life is t, then

• A. \[t={{t}_{1}}+{{t}_{2}}\]
• B. \[\frac{1}{t}=\frac{1}{{{t}_{1}}}+\frac{1}{{{t}_{2}}}\]
• C. \[t=\frac{2{{t}_{1}}{{t}_{2}}}{{{t}_{1}}+{{t}_{2}}}\]
• D. \[t=\frac{{{t}_{1}}+{{t}_{2}}}{2}\]