They were exposed to biased information, so they didn't know the true story.
A. If they got unbiased information, they could know the true story.
B. If they had unbiased the information, they could have known the true story.
C. If they had been exposed to unbiased information, they would have known the true story.
D. If they have exposed to the unbiased information, they could have seen the true story.