"And it was not Adam who was deceived, but the woman being deceived, fell into transgression." 1 Timothy 2:14
Adam choose to sin.
Why?
The temptation was "you won't die...you will be like God, knowing good and evil"...
The lie that Eve was deceived with was "you shall not die"... The part about being "like God" in the instance of knowing good and evil, wasn't a lie. After all, we certainly do know about good and evil...
So, Adam, because we are told he was not deceived, must have realized that he would die, but nonetheless decided that being like God and knowing good and evil were worth it.