The correct answer is: C. Either I or II follows
The statement does not provide enough information to determine whether conclusion I or conclusion II is definitely true. It is possible that the 25 independent MLAs will join XYZ party, but it is also possible that they will join some other political party. The statement only tells us that they are considering various options and will join one party only.
Conclusion I: The 25 independent MLAs will join XYZ party in a short period of time.
This conclusion is not necessarily true. The statement does not say that the 25 independent MLAs will join XYZ party. It only says that they are considering various options and will join one party only. It is possible that they will join some other political party.
Conclusion II: The 25 independent MLAs will join some other political party in a short period of time.
This conclusion is also not necessarily true. The statement does not say that the 25 independent MLAs will join some other political party. It only says that they are considering various options and will join one party only. It is possible that they will join XYZ party.
Therefore, either conclusion I or conclusion II could be true, but neither conclusion is definitely true.