Answer is B. ABAB. Hope it helped you, and have a great day.
-Charlie
This would be more of a chemistry question. Remember magnesium has a charge of 2+, and would need to hand off its two extra electrons. Fluorine can only take one electron at a time, so there needs to be two fluorines to take one magnesium's 2 electrons.
With lithium, it has a +1 charge, so it has one extra electron, which it can hand off to just 1 fluorine atom.
Another way of looking at this is:

+ 2

= MgF2 (the charges must balance out to zero)

+

= LiF (the charges balance out to zero)
Answer:
B. Direction
Explanation:
Speed is a scalar quantity and doesn't keep track of direction : Velocity is a vector quantity and is direction aware.
Acceleration is the rate of change of the velocity of an object that is moving. This value is a result of all the forces that is acting on an object which is described by Newton's second law of motion. To determine acceleration, we need to know the initial velocity and the final velocity and the time elapsed. From the given values, we need t o calculate for the initial velocity. We use some kinematic equations. We do as follows:
x = v0t + at^2/2
60 = v0(6) + a(6)^2/2
60 = 6v0 + 18a (EQUATION 1)
vf = v0 + at
15 = v0 + a(6)
15 = v0 + 6a (EQUATION 2)
Solving for v0 and a,
v0 = 5 m/s
a = 1.7 m/s^2