German submarines aimed to attack ships that were carrying

a. weapons to the allies.

b. passengers to the united states.

c. food to the central powers.

d. oil to mexico.

A. Weapons to the allies.

Although it did happen, the U-Boats objectives were to stop the Allies war effort such as weapons rather than passenger ships which had passengers. The Central powers are the Axis / Germany as for Oil to Mexico, I doubt many U-Boats made it to the USA.