Presence of Tail Water in a Gravity Dam

Presence of tail water in a gravity dam
i. increases the principal stress
ii. decreases the principal stress
iii. increases the shear stressiv) decreases the shear stress
The correct answer is

A) (i) and (iii)
B) (i) and(iv)
C) (ii) and (iii)
D) (ii) and (iv)