bhanupra wrote:Hi Ron/Stacey,
In the option d , why 'have been dated' is correct ?
It sounds good to me, but why present perfect tense is used in this case.
in describing a past event that is no longer occurring, we can use either the present perfect or the simple past. the difference between the two is one of semantic meaning:
* the present perfect
(has/have VERBed) is used if the event still has a tangible impact or influence on, or relevance to, the present state of affairs
* the simple past
is used if the event does NOT
have any tangible impact/influence/relevance in the present.
note that, in many cases, either of these tenses could be used to describe exactly the same event in exactly the same timeframe!
here's an example: imagine that you are talking to a guy, at a bar, who has had 3 marriages. (he is currently divorced.)if the two of you are actually talking about marriage
, he will probably say "i have been
married three times".if the two of you are NOT directly talking about marriage or its consequences
-- for instance, he is just enumerating members of his family -- he will probably say "i was
married three times".
both of these are correct -- in terms of both grammar and semantics.
in the example at hand, the present perfect probably makes a little bit more sense, since the findings clearly have direct relevance to the situation being discussed at present. however, it would certainly not be incorrect to use the simple past (although that usage would suggest that the findings no longer have relevance, possibly because they have been superseded by some more recent findings).
here are some words that i wrote on another thread, but which are also appropriate here:
ronpurewal wrote:for non-native speakers of english, verb tenses are the single hardest and most subtle aspect of english grammar.
this is actually the case in pretty much all languages of the world -- verb tenses tend to encode incredibly subtle and specific information, information that, frustratingly enough, varies wildly from language to language.
what this means is that, to truly understand the usage of english tenses in full, you actually have to learn to start thinking like a native speaker of english. this is not easy to do. (by contrast, you don't have to think like a native speaker of english to understand things like subject-verb agreement or parallelism; you just have to be able to analyze things with a sufficiently mechanical outlook and with sufficient attention to the semantic meaning of the sentence.)