The widely accepted big bang theory holds that the
universe began in an explosive instant ten to twenty
billion years ago and has been expanding ever since.
In the e- gmat application file -1, a similar question is asked. and it is told that if "since" is there in the sentence ,"past/present perfect" is correct choice. However, in the question above , the present perfect continuous tense is used. I do understand that meaning of sentence intends a continuous action, however, "ever since" also tells us that action is started in past and continues in present. this is perfect case for present perfect tense. then why presnt perfect is not correct answer choice.
Also clarify whether the present perfect as well as present perfect continious are both right forms of tense that should be used in sentence like the one above.
Thanks for posting your query here.
The present perfect tense is used to refer to an action that is complete, while the present perfect continuous tense is used to refer to an action that is not yet complete.
For example:1. She has written a book.
2. She has been writing a book.
The first means that she has finished writing the book, and the second means that she is still writing the book.
In this question, the meaning is not that the universe has finished expanding, but that it is still expanding. So, we need the present perfect continuous tense.
Both forms of tense are correct and should be used in accordance with the intended meaning of the sentence.
I hope this helps to clarify your doubt!
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