Answer:
1). Slope of line = -2.
2). Option D is correct.i.e.,

3). Option B is correct.i.e., constant of variation is -2.
Explanation:
1).
Given: A line and its two points in graph
To find: Slope of line in graph
Formula used to find Slope from two points is given by,

Points are ( 0 , 3 ) , ( 1 , 1 )

Therefore, Slope of line = -2.
2).
Given: Points ( -2 , -3 ) & ( 1 , 1 )
To find: Slope of line which passes through given points.
We again use formula of Slope from two points,

Therefore Option D is correct.i.e.,

3).
Given: equation , -4y = 8 x
To find: Constant of variation
The constant of variation is the relationship between variables that does not changes
Consider,
-4y = 8x
Transpose -4 to RHS

y = -2x
So, if we put any value of x we get value of y which is -2 times value of x.
⇒ Constant of variation is -2
Therefore, Option B is correct.i.e., constant of variation is -2.