Answer: Jesus said that those who believe the preaching of the Good News AND who are baptized will be saved, (verse 16).
MORE INFORMATION AND/OR OTHER SCRIPTURE REFERENCES:
Belief alone is not enough. The kind of belief, or faith, that Jesus wants is an obedient faith. It is the kind of faith that extends to the Father, Who has given the commands of salvation through His Son:
John 12:44-46: "Then Jesus cried out, ‘When a man believes in Me, he does not believe in Me only, but in the One Who sent Me. When he looks at Me, he sees the One Who sent Me. I have come into the world as a light, so that no one who believes in Me should stay in darkness.'"
Matthew 7:21: "Not everyone who says to Me, ‘Lord, Lord,' will enter the kingdom of heaven, but only he who does the Will of My Father Who is in heaven."
Even the demons know and believe that Jesus is the Son of God:
Luke 4:41: "Moreover, demons came out of many people, shouting, ‘You are the Son of God!' But He rebuked them and would not allow them to speak, because they knew He was the Christ."
James 2:19: "You believe that there is One God. Good! Even the demons believe that--and shudder."
