The propositions are:
A. an electron is given offB. an electron is absorbed and turned into a neutronC. an atom splits into two piecesD. an alpha particle combines with a small atom to make a larger one
Radioactive nuclei emit three kinds of radiation called by alpha, beta, and gamma, which are respectively: helium nuclei, electrons (and positrons), and photons (with high energy).
In alpha radioactivity, the nucleus seeks stability by emitting a nucleus of helium (two protons and two neutrons) called also an alpha particle.
based on the definition we can exclude A and B because alpha decay has nothing to do with electrons.D is false because the alpha particle is emitted and does not combine
So, C is the right answer since the radioactive atom will split into an alpha particle and a smaller atom.