What do you say if someone tells you they think science proves Christianity to be false?

This was the final exam question for my Core 300 class in at Spring Arbor University, Biblical History and Literature, taught by Dr. Chuck White.  All of this information is either from lectures or ideas from How Now Shall We Live by Charles Colson.

Science can be very unreliable -- it is not always certain.
There is evidence against it, and there is evidence in God's favor!

Scientists sometimes "cheat" in their attempts to prove theories.  They will sometimes do whatever is necessary to show what they believe to be the truth.  Take Miller's experiments for example.
In Miller's experiments, scientists made what they called "life" (actually all they made was a form of amino acids -- some of which are necessary components for life) from chemicals in an effort to prove that life did not have to be a result of God.  However:

David Hume was a philosopher and an historian, and also a skeptic of any evolutionary theory.
A Skeptic's Dictionary - contains an outline of Hume's views on miracles
The Internet Encyclopedia of Philosophy's article "Modern Skepticism" - discusses Hume's skepticism
Basically, David Hume's beliefs include:

What are the chances of the world coming about by chance?
There is too much chance involved to be confident of the Big Bang, evolution, etc.

There is a limit to selection.

Evolution would have to be somewhat gradual.  One species could not have just borne another completely different species.  But gradual evolution is impossibly, due to the irreducible complexity thory.  For example:

The 12-step argument for Christianity
  1. There was a Jesus of Nazareth.
  2. Gospels are reasonably historically accurate.
  3. Jesus thought he was God.
  4. Jesus either was God or wasn't, and he either knew who he was or didn't.
  5. Jesus said he would prove that he was God by rising from the dead.  (Matt 12:40)
  6. Jesus was crucified by Pontius Pilat and did die on the cross.  (John 19:33-34)
  7. On the third day after Jesus died on the cross, his tomb was empty.
  8. Jesus was seen alive by more than 500 people.
  9. His disciples came to believe he was God.
  10. The explanation that Jesus rose from the dead is the most reasonable explanation of data.
  11. If Jesus told the truth when he claimed he would rise from the dead, it is reasonable to believe he told the truth when he claimed to be God.
  12. If Jesus is God of the universe, he should be God of my life -- and yours!