(A) Litigate - go to law; be a party to a lawsuit.
(B) Ease - absence of difficulty or effort.
(C) Conflict - a serious disagreement or argument, typically a protracted one.
(D) Frustrate - prevent (a plan or attempted action) from progressing, succeeding, or being fulfilled.
The given word Discomfit means make (someone) feel uneasy (opposite of option [B] ) or embarrassed. It is from the feeling of uneasiness or embarrassment that frustration stems. Hence the correct synonym of the given word is option (D) Frustrate.