There may be no satisfactory answer to this question. The Bible is clear about the exclusive claims of Christ (see Jn 14:6). Yet we also know God is merciful and absolutely just. It would seem to contradict what we know of his nature if he did not account for the disadvantages of those who, through no fault of their own, have never heard of Jesus.
From another perspective we have to say that even those who have heard the name of Jesus do not deserve to be saved. Salvation is always the result of God’s love for us, not our love for him. It is his grace—not our efforts—that saves us.
Still, God’s grace requires a human response. Christians have a responsibility to make Christ known in all the world so people have the opportunity to respond (see Mt 28:19–20). Ultimately, we can trust God to judge the world justly.