I hope I've misunderstood what you are saying. You are not saying that ALL people know of Christianity and that ALL people have been given a chance to accept are you?
This is the passage from Romans 1:
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18] For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who hold the truth in unrighteousness;
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19] Because that which may be known of God is manifest in them; for God hath shewed it unto them.
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20] For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse:
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21] Because that, when they knew God, they glorified him not as God, neither were thankful; but became vain in their imaginations, and their foolish heart was darkened.
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22] Professing themselves to be wise, they became fools,
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23] And changed the glory of the uncorruptible God into an image made like to corruptible man, and to birds, and fourfooted beasts, and creeping things.
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24] Wherefore God also gave them up to uncleanness through the lusts of their own hearts, to dishonour their own bodies between themselves:
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25] Who changed the truth of God into a lie, and worshipped and served the creature more than the Creator, who is blessed for ever. Amen.
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26] For this cause God gave them up unto vile affections: for even their women did change the natural use into that which is against nature:
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27] And likewise also the men, leaving the natural use of the woman, burned in their lust one toward another; men with men working that which is unseemly, and receiving in themselves that recompence of their error which was meet.
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28] And even as they did not like to retain God in their knowledge, God gave them over to a reprobate mind, to do those things which are not convenient;
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29] Being filled with all unrighteousness, fornication, wickedness, covetousness, maliciousness; full of envy, murder, debate, deceit, malignity; whisperers,
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30] Backbiters, haters of God, despiteful, proud, boasters, inventors of evil things, disobedient to parents,
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31] Without understanding, covenantbreakers, without natural affection, implacable, unmerciful:
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32] Who knowing the judgment of God, that they which commit such things are worthy of death, not only do the same, but have pleasure in them that do them.