The correct option is B 90∘
Ray OS stands on the line POQ, so, ∠POS+∠SOQ=180∘ (Linear pair)
Given, ∠POS=x
Hence, x+∠SOQ=180∘
⇒∠SOQ=180∘−x
Now , ray OR bisects ∠POS
Hence, ∠ROS=12×∠POS.
⇒12×x=x2
Similarly, ∠SOT=12×∠SOQ
⇒12×(180∘−x)=90∘−x2
Hence, ∠ROT=∠ROS+∠SOT
⇒x2+90∘−x2=90∘