Yes, yes it is; well done.
I think it’s d because it’s like similar
Answer: 
Step-by-step explanation:
Given
The height of the cylinder is 
The volume of the cylinder is 
The volume of the cylinder is the product of area and height

Insert the values

Thus, the area of the cross-section is 
Answer:
B
Step-by-step explanation:
A graph is only a function when there is only one y value for each x value.
A trick is to draw a line through some points on the x-axis, and if the line goes through more than one point. Then it is not a function. (See picture)
Sorry, not all the lines are straight, but you get the point. B is the only one that doesn't have more than one point on the lines I drew.