According to the formula you have given us to work with . . .
1). The airplane's acceleration is
(80 m/s north - zero) / (20 sec) = 4 m/sec^2 north
2). For the cyclist:
(V-final - zero) / 20sec = 0.5 m/s^2 south
Multiply each side by 20s : V-final = 0.5 m/s^2 south x (20sec) =
10 m/s south
Answer: The given statement is true.
Explanation:
It is known that due to increase in temperature ice melts. Therefore, during ice age there is also melting of ice and solid state of water changes into liquid state of water.
Therefore, this water moves from its initial place and changes its position result in the change of land and specific areas.
Thus, we can conclude that the statement during an ice age, land can move and specific areas can be permanently changed is true.
I think that the answer is probably b-the liquid water particles turn into water vapor that spreads in the air
The chemical formula of oxalic is 
When oxalic acid reacts with water, first, oxalic acid removes one proton and results in the formation of mono acids.
After that, in second step, oxalic acid in aqueous solution removes another proton which shows it is a polyprotic acid.
The chemical equations are: (the reactions occurs in two steps due to presence to hydrogen atoms).
When one proton is removed:

When another proton is removed:

The dissociation of oxalic acid in water in shown in the image.
Answer:
Getting coated with tarnish
Explanation:
Silver, the original substance is combining with a new substance tarnish to make a whole new chemical.