Correct Answer: strangely

Solution : The second option is the correct answer.

Strangely means unusually or unexpectedly; it fits well with the idea of feeling elated in an unexpected manner.

The meanings of the other options are as follows:

• Commonly means frequently or generally occurring; happening often.
• Customarily means according to established customs or usual practices.
• Typically means in a manner that is characteristic or representative of a particular kind; usually.

Therefore, the complete sentence is: I felt strangely elated at the news.