【正确答案】 A

【答案解析】The opposite of contentious (quarrelsome, belligerent) is amenable (readily brought to yield, tractable).
Note that contentious derives from the verb to contend (to struggle or argue), not the adjective content.
Think of "a particularly contentious argument./

【正确答案】 B

【答案解析】The opposite of a debacle (downfall; failure; collapse) is a success.
Think of "the Wall Street debacle of 1987./