D. They signed a treaty with Spain
The correct answer is war
The notion of war is related to terms such as combat, battle, fight, fight or confrontation. In general, all of these concepts are interchangeable and synonymous, although each has a specific use that is better suited to the case. For example, it is correct to speak of "combat between boxers", but not of "war between boxers".
War refers, in its most usual sense, to armed struggle or war conflict between two or more nations or bands. It implies the disruption of a state of peace and gives rise to a confrontation with all types of weapons and which usually causes a high number of deaths.
I believe the answer is: They worried about having to take part in future wars.
At that time, the united states senates prefer to take the position as a neutral force that want to avoid any intervention toward other countries' problems. This stand is taken away the moment the Japanese army decided to initiate an attack to the pearl harbour.
