Read the excerpt from The Dark Game.

But how would Hall get that telegram? That would take some doing, he admitted. Then Hall remembered Mr. H., one of his trusted operatives. It was Mr. H. who had alerted MI8 to the suspicious activities of Sweden's chargé d'affaires in Mexico City, Folke Cronholm. Sharp-eyed Mr. H. had noticed that Cronholm was making frequent visits to the telegraph office, far more visits than one would expect from a representative of the Swedish government, given the limited relationship between that government and Mexico.

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

Folke Cronholm was spying for the Allied nations.
Folke Cronholm was a German diplomat.
Folke Cronholm was secretly working for the Germans.
Folke Cronholm was receiving many personal telegraphs