In extraordinary circumstances,

[angliholic]

In extraordinary circumstances, some choose to risk their lives for others.
In extraordinary conditions/situations, some choose to risk their lives for others.


Do the above versions all sound good? If yes, are there any subtle differences semantically? Thanks.

[Teia]

In extraordinary circumstances, some choose to risk their lives for others.
In extraordinary conditions/situations, some choose to risk their lives for others.


Do the above versions all sound good? If yes, are there any subtle differences semantically? Thanks.

Under extraordinary circumstances....

In extraordinary conditions/situations, some choose to risk their lives for others.

I think that these words are relative synonyms and you can use the one you wish.