Who was the first president? i need cuz i can't think right now for some reason.

Which best explains why the allies employed the europe first strategy during world war ii? a.japan was a greater threat than germany to the allies. b.japan received military assistance from germany, so the allies needed to defeat germany first. c.the allies wanted to ensure that germany did not continue to conquer european territory. d.the allies needed japan’s vast stockpile of weapons to defeat germany.