Which of the following rays are not electromagnetic waves?

Neutrino is a particle which $\qquad$

When $_{90}^{228}Th$ transforms to $_{83}^{212}Bi$,the number of emitted $\alpha$- and $\beta$- particles is,respectively:

$U^{238}$ decays into $Th^{234}$ by the emission of an $\alpha$-particle. There follows a chain of further radioactive decays,either by $\alpha$-decay or by $\beta$-decay. Eventually,a stable nuclide is reached,and after that,no further radioactive decay is possible. Which of the following stable nuclides is the end product of the $U^{238}$ radioactive decay chain?

$A$ radioactive element emits two $\beta$-particles and one $\alpha$-particle. The resulting daughter nucleus is ...

In the nuclear reaction $6C^{11} \rightarrow 5B^{11} + \beta^+ + X$,the particle $X$ is .......