Sentence:  The form of Christianity to which they were <WSD>exposed</WSD> was for some the Protestantism of the older stock , for others the Protestantism of the nineteenth-century immigration ; for still others , mostly of the nineteenth-century immigration , it was Roman Catholicism , and for a small minority it was Eastern Orthodoxy . 
Meaning of the word marked with <WSD> tags:  expose or make accessible to some action or influence