There is a passage with some blanks to fill in with proper words.
The passage is mainly about a veterinarian who always felt hard to comfort the pet owners after performing the euthanasia of pets. But once after he again performed one on a dog, a four-year- old boy's words, to his feeling, were really comforting.
Here is the extract of the passage, where I feel confused about the option of two words for a blank.
"...Making this final decision is painful, and I have often felt powerless to comfort the sad owners. But that was ________ I met Shane.(referring to that little boy who later said comforting words）"
A. before B. until
The answer is "before", then isn't "until" right in the sentence? Thanks for your reply!
Informally, natives would accept either, but 'before' is the more standard choice in this instance.