Four people read 6to 8 books.
To find a slope we have to use this equation:
(y2 - y1 )/(x2 - x1)
and we have two x's and y's
so we will put them in their places....so (1-(-5))/(4-2)
and we will get 6/2 which is 3
Its A.3
.............

by using the integration formula
we get,

now put the value of t=\sin\theta in the above equation
we get,

hence proved