B

Step 1: Understand the types of particles involved in radioactive decay. Common emissions include alpha (B1) particles (helium nuclei), beta (B2) particles (electrons), and gamma (B3) rays (photons).
Step 2: Identify the charge and mass of emitted particles.
- Alpha particles carry a positive charge and are made of 2 protons and 2 neutrons.
- Beta particles are negatively charged electrons.
- Neutrons are neutral and do not get emitted in decay directly.
Step 3: Determine the effect of a magnetic field on these particles.
- Positively charged particles (alpha) and negatively charged particles (beta) are deflected by magnetic fields. Neutrons, being neutral, are not deflected.
Therefore, the correct answer is B, as it includes all relevant particles (electrons and protons) that get deflected.