Correct option is E
The best word that can fit into the blank without altering the intended meaning is "speculate." The sentence would then read: "It is idle to speculate what the consequences would have been." To speculate means to form opinions or theories about something without having all the information, which fits the context of wondering about the consequences without knowing for sure.
Manipulate: handle or control (a tool, mechanism, information, etc.) in a skillful manner.
Articulate: having or showing the ability to speak fluently and coherently.
Nourish: provide with the food or other substances necessary for growth, health, and good condition.
Cherish: protect and care for (someone) lovingly.
Speculate: review in an idle or casual way and with an element of doubt or without sufficient reason to reach a conclusion