Unless you live(d) in a time and place where Christian teachings were unavailable to you. Which accounts for a large majority of the humans who have ever lived.
Which is a problem for some Protestants who insist that only Christians can be saved... but not necessarily for Catholics. The belief that only Christians can be saved has actually been condemned by the Catholic Church as a heresy (Feeneyism, after the 20th century American priest, Leonard Feeney, who most famously espoused it)
According to Catholic teaching, non-Christians can be saved if (1) they are "invincibly ignorant" (i.e. their ignorance of the truth of Christianity is not their own fault), and (2) they have an "implicit desire" for the Christian God
