What's the call?

[shocker]

This is off the 2002 NFHS exam.
If substitute B12 is on A's side of the neutral zone when the ball is snapped, it's an encroachment foul.
Answer is false. So what is the call?

Rules definition is as follows:

SECTION 30 PLAYER DESIGNATIONS

ART. 15 . . . A substitute is a team member who may replace a player or fill a player vacancy. A substitute becomes a player when he enters the field and communicates with a teammate or an official, enters the huddle, is positioned in a formation or participates in the play. An entering substitute is not considered to be a player for encroachment restrictions until he is on his team's side of the neutral zone. A team member entering the field to fill a player vacancy remains a substitute until he is on his team's side of the neutral zone.