Answer:
A.) The Germans often sent important messages concerning their war efforts to their ambassador in Washington, D.C.
Step-by-step explanation:
In order to infer information from a text, such information has to be implied in it or at least there have to be enough hints for it in the text. In this excerpt there's no information that relates what is being stated with the ideas in options B, C, D. While for the idea in option A there's plenty of information available, even stating the cable was for communications between the germans and ther ambassador, therefore A is the correct answer.