都选B.to do在这里面都作定语.至于何时用被动语态,注意下例解释
附：⒈不定式作定语
不定式在句中作定语,置于被修饰的名词或代词之后.如：
①The next train to arrive is from Washington.
②Have you anything to be taken to your sister?
③Do you have anything to say on the question?
④Would you please give me some paper to write on?
⑤My wish to visit France has come true at last.
不定式短语作定语和被修饰词之间表示以下关系：
(1)表示将来的动作（例①）.
(2)与被修饰词之间有动宾关系,如是不及物动词,则需加介词（例④）.
(3)与被修饰词之间有动宾关系,同时与句中其它词之间又有逻辑上的主谓关系时,尽管有被动含义,却仍 用主动语态（例③）；如只有动宾关系,而无逻辑上的主谓关系,则需用被动语态（例②）.
(4)不定式作定语时,一般可转换为定语从句,例①to arrive=that will arrive.