https://reurl.cc/93agOY
I agree that grammatically 'to accept' is the only really good one, but the
present tense (if you used this sentence now) would imply that no country
does, and Taiwan is about to, or perhaps has just done so. To reflect the
facts, they would both need to be in the past:
Was Taiwan the first country to have accepted . . .

Unless there's something fundamentally wrong with allthe answers, students in Taiwan will simply pick themore acceptable one(s). Unlike us, they don't usually take the liberty of rewriting test questions ;^)