scrimmage kick

[bicepsforyou]

The answer is b

[golfdesigner]

Didn't quite make the Wed time constraint but...If the choices are limited to A and B, B is correct, otherwise to make a short story long:

Art. 2 . . . A kick ends when a player gains possession or when the ball becomes dead while not in player possession.

When any legal free kick or scrimmage kick:
1. Which is not a scoring attempt or which is a grounded scoring attempt, breaks the plane of R’s goal line.

A kick is a loose ball play--
e. When any loose ball:
1. Is simultaneously caught or recovered by opposing players.
2. Is on the ground motionless and no player attempts to secure possession.
3. Touches, or is touched by, anything inbounds other than a player, substitute, replaced player, an official, the ground or authorized equipment. In this case the ball will be put in play in accordance with the procedure for an inadvertent whistle as in 4-2-3b.

f. When the kickers catch or recover any free kick anywhere, and when the kickers catch or recover a scrimmage kick beyond the neutral zone and when the kickers are first (i.e., before any touching by the receivers) to touch a scrimmage kick after it has come to rest beyond the neutral zone and between the goal lines.

g. Following a valid or invalid fair-catch signal given by any member of the receiving team when a scrimmage kick or free kick is caught or recovered by any member of the receiving team beyond, in or behind the neutral zone.

[JGF6]

(NF) A scrimmage kick also ends when the ball comes to rest and K touches it. In this case they do not have to possess it. 4.2.2f

[wisref2]

Rule 2 nearly always answer questions like this - always look there first.

Kicks end, as in 2-23-2: A kick ends when a player gains possession or when the ball becomes dead while not in player possession.

This is also addressed in Football Fundamentals - a must read every season, and several times a season:
IV-1: A kick always ends as soon as any player secures possession.

Also, try to get in the habit of using proper terminology. A kick ends, but it doesn't necessarily become dead. The proper answer to your question of "When is a scrimmage kick officially dead," is not included in your choices. It is covered in Fundamental IV-5: "Any scrimmage kick which is not a scoring attempt becomes dead when it breaks the plane of R's goal line."