(A) - (II) "hidden agenda" → The sentence suggests she has a secret reason or ulterior motive for not revealing information about the letter.
(B) - (IV) "at someone's beck and call" → Describes employees who must be constantly available to fulfill the boss's demands whenever she wants.
(C) - (I) "at the receiving end" → Refers to being the recipient of criticism or negative treatment from the press.
(D) - (III) "left to my own device" → Expresses the desire to work independently and make one's own decisions without constant supervision.
Hence, Option 4: (A) - (II), (B) - (IV), (C) - (I), (D) - (III) → Each idiom perfectly captures the essence of its corresponding sentence: hidden agenda for undisclosed motives, beck and call for constant availability, receiving end for being criticized, and left to own device for independence → correct