meaning of oath

[Deorra]

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #259 "US Government Questions Test (7)", question 3

If an alien is offered American citizenship, he/she must take an oath of ......... in order to proceed with the next course of action.

(a) country
(b) government
(c) allegiance

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #259 "US Government Questions Test (7)", answer 3

If an alien is offered American citizenship, he/she must take an oath of allegiance in order to proceed with the next course of action.

Correct answer: (c) allegiance
_________________________

what if oath?

Deorra

[Conchita]

An oath is swearing that you are telling the truth. We can say something on oath or take an oath.

To take/swear an oath of allegiance is to promise to be faithful.

An oath can also be a swear word.

[Violino]

Is 'oath' similar to 'promise' then?
Can I say: "... he/she must promise alligance..."?