This is a terrible topic. The non-underlined part says that in June 1981, some people claimed to have visions of Virgin Mary ……, who then has continued to appear to them over the ensuing years. If Mary were to appear in later years, how would they say it in an earlier time of June 1981? This like a child’s play who often mixes up tenses as saying I saw tomorrow. In addition, the second part containing the subordinate clause unnecessarily shifts to simple present and present perfect from the past tense of the main clause.
The point the topic wants to prove perhaps is the use of
who or whom and the use of past perfect. Since the visions must have occurred earlier than their claim, obviously we are required to use
“to have had” along with a simple past, which is sufficient to indicate prioress. ‘Had clamed’ is very wrong.
On the use of
‘who or whom’, we can see that the later part of the sentence has verb
‘has continued “which needs to have a subject or a subject pronoun pronoun such as
who rather than an object pronoun ‘
whom’.
On the difference between
'to have had and to have': when you claim
'to have visions', it means here that you are having visions just then as you make that claim. On the contrary, when you claim
'to have had visions', it indicates that you had the visions before you have come forward to make the claim, which is the correct context.
As such, not withstanding the terrible handling of the tenses in the non-underlined parts, structurally A will be the correct one .