The correct option is A 360∘
In the quadrilateral PQRS,
∠P+∠Q+∠R+∠S=360∘
⇒120∘+80∘+60∘+∠S=360∘
⇒∠S=100∘
∠P+ext∠P=180∘ [Linear Pair]
⇒120∘+a=180∘
⇒a=60∘
Similarly,
∠Q+ext∠Q=180∘ [Linear Pair]
⇒80∘+b=180∘
⇒a=100∘
And,
∠R+ext∠R=180∘ [Linear Pair]
⇒60∘+c=180∘
⇒a=120∘
∠S+ext∠S=180∘ [Linear Pair]
⇒100∘+d=180∘
⇒d=80∘
⇒a+b+c+d=60∘+100∘+120∘+80∘
⇒a+b+c+d=360∘