Questions in nuclei

Select	Question
	The phenomenon of radioactivity is
	If half life of radium is 77 days. Its decay constant in day will be
	In a radioactive reaction $_{92}{X^{232}}{ \to _{82}}{Y^{204}}$, the number of $\alpha - $ particles emitted is
	In a sample of radioactive material, what fraction of the initial number of active nuclei will remain undisintegrated after half of a half-life of the sample
	Consider two nuclei of the same radioactive nuclide. One of the nuclei was created in a supernova explosion 5 billion years ago. The other was created in a nuclear reactor 5 minutes ago. The probability of decay during the next time is