A radioactive source gives out three forms of radiation, R, S and T. The diagram illustrates an experiment arranged to investigate the penetrating ability of R, S and T. What are the identities of the radiations R, S and T?
- AR: $\alpha$-particles, S: $\beta$-particles, T: $\gamma$-rays
- BR: $\alpha$-particles, S: $\gamma$-rays, T: $\beta$-particles
- CR: $\beta$-particles, S: $\alpha$-particles, T: $\gamma$-rays
- DR: $\gamma$-rays, S: $\beta$-particles, T: $\alpha$-particles