Answer:
C. It does not participate in a decay series. 
Step-by-step explanation:
From this statement, we can deduce that a radioisotope that forms a stable isotope after it undergoes radioactive decay suggests that it does not participate in a decay series. 
- It could have emitted any form of radioactive particles which can be alpha or beta. 
- We do not know if it has a long or short half life because the value is not given. 
- But since the radioactive decay in one step produces a stable isotope, we can conclude that it did not participate in a decay series. 
- A decay series involves a radioactive decay in multiple steps.