If You Want to Detect Lies

If you want to detect lies:

A) you can see if people speak at a higher pitch; this is a sure sign of lying.
B) there is no one cue you can look to for certain evidence of lying.
C) you should give up; liars don't do anything differently from truth tellers.
D) you should look at whether or not the potential liar looks you in the eye; this is a sure sign of lying.