Awar between two us allies is a matter of a - foreign policy b - domestic policy

Correct

Explanation:

Foreign policy refers to a country's relationships and actions with other countries.  "Foreign" means that it has do with countries outside of the United States.  So if two US allies become embroiled in a war with each other, that pertains to US foreign policy -- dealings with other nations.

Domestic policy refers to a country's programs and actions within its own borders.  "Domestic" stems from the Latin word "domus" which means "house."  So "domestic" affairs are those matters taking place inside your own "house" -- or in the case of a nation, inside your own nation.

c) troops march forward in close formation against newer, more accurate weapons