The batter (B1) hits a grounder between 1st and 2nd base. The first baseman fields the ball and now it is a foot race to try to beat B1 to first base.  B1 arrives at first base just ahead of the first baseman, but B1 runs overtop first base without tagging the bag. The first baseman touches first base just after B1 stepped over the bag. 

 

What is the base umpire's initial call on this play:

A) "Out", the first baseman touched first base (while securely holding the ball) before B1 touched first base

B) "Safe", B1 passed first base before it was touched by the first baseman