Which of two.
The word 'whether' is correct and usable in written English. It can be used to introduce a clause when you want to express a choice between two possibilities, or when introducing an indirect question, e.g. "I don't know whether I should leave now or stay longer.".
Access to treatment should not depend on whether someone can spare the money.
Unlike the most reliable form of protection, a condom, it is the woman, not the man, who makes the ultimate choice about whether to use the gel.
What happened four months ago is forgotten, whether that's good, bad or indifferent.
There was of course no way of knowing whether you were being watched at any given moment.
"I am very aware that some have questioned whether the number plates were in some way a prank.
Whether the Earth was created in 7 days, or 7 actual eras, I'm not sure we'll ever be able to answer that.
"It makes me very worried for her, because I do not know whether she is alive or where she might be".
Since I tried Ludwig back in 2017, I have been constantly using it in both editing and translation. Ever since, I suggest it to my translators at ProSciEditing.
Justyna Jupowicz-Kozak
CEO of Professional Science Editing for Scientists @ prosciediting.com