Question

On January 16, 1917, in a clear attempt to convince the Mexican government to help Germany in the war, Arthur Zimmermann, the German foreign secretary, sent a telegram to Count von Bernstorff, the German ambassador in Washington. The foreign secretary wanted to be certain that this message reached von Bernstorff, so he made arrangements for it to be carried aboard a U-boat to Sweden and from there to Washington through diplomatic channels.

—The Dark Game,
Paul Janeczko

Which inference can a reader make based on the information in the passage?

The message Zimmermann wanted to send to von Bernstorff was very important.
Count von Bernstorff was expecting the message.
U-boats were designed to transport messages securely.
Zimmermann wanted to reach out to the Mexican government for support.

Answer 1

The message Zimmermann wanted to send to von Bernstorff was very important.

Reason: Zimmermann "wanted to be certain" it reached von Bernstorff and arranged special, secure transport (a U-boat to Sweden and then diplomatic channels), which implies the message's high importance. The other choices are not supported (one is explicitly stated as motive, one is not implied, and one wrongly generalizes U-boats' purpose).