The radioactive decay of thorium-232 occurs in multiple steps, called a radioactive decay chain. The second product produced in this chain is actinium-228. Which of the following processes could lead to this product starting with thorium-232?
(a) Alpha decay followed by beta emission
(b) Beta emission followed by electron capture
(c) Positron emission followed by alpha decay
(d) Electron capture followed by positron emission
(e) More than one of the above is consistent with the observed transformation.