The sentence indicates that the marriage between a princess and a commoner caused uproar among royalty, implying that the union was socially unequal and considered unsuitable.
The correct term here is "misalliance", meaning a marriage or union regarded as unsuitable or ill-matched, especially from a social standpoint.
Option (A) "missalliance" is simply a misspelling of the correct word "misalliance" and is therefore incorrect.
Option (C) "elopement" means running away secretly to get married, but the sentence focuses on the mismatch rather than the act of eloping.
Option (D) "romance" is far too general and does not convey the sense of social inappropriateness.
Therefore, (B) is correct, as it precisely matches the idea of a socially controversial marriage.