(A) to sit on the fence - (III) delay in making a decision
(B) a sitting duck - (IV) an easy target for attack or criticism
(C) sit pretty - (I) to be in a good position
(D) sit tight - (II) to not take any action/remain in a place
The CEO's sudden resignation threw the board into a tailspin.
What does the idiom "threw into a tailspin" mean?