(a) The correct option is (B) Block B.Below figure shows the block A slides down the ramp without the friction. The acceleration of A block is vertical component g (g cosθ) which is always less than the value of g.

Since the block B falls vertically without friction at the same instant, so the acceleration of the block B will be equal to the acceleration due to gravity g.
From the above observation, acceleration of the B block is greater than the acceleration of A block. Therefore block B reaches the bottom first. Thus option (B) is correct.
(b) The correct option is (C) they arrive with the same speed.
From equation of motion we know that,
v2 = u2+2gh …… (1)
Where u is the initial speed of the object, v is the final speed of the object and g is the acceleration due to gravity.
Initial speed of both the object is zero (u=0).
Substitute initial speed of both the object (u=0) in the equation (1), then equation (1) reduces to,
v2 = u2+2gh
 = 0+2gh
So, v = √2gh …… (2)
Since for both the object the value of acceleration due to gravity g and height h from where they fall are equal, therefore from equation (2) we observed that the speed at which both the block reaches at the bottom will be same.
Thus option (C) is correct.
(c) The correct option is (B) block B.
Below figure shows the block A slides down the ramp without the friction. The acceleration of A block is vertical component g (g cosθ) which is always less than the value of g.




Since the block B falls vertically without friction at the same instant, so the acceleration of the block B will be equal to the acceleration due to gravity g.
From the above observation, acceleration of the B block is greater than the acceleration of A block. Thus option (B) is correct.