Can some one help explain why the past tense is prefered to past perfect tense there please?
A, Recently scientist learned about the changes in earth that had happened during the last ice age. wrong
B, Recently scientist learned about the changes in earth that happened during the last ice age. right
It says the two event - "learn" and " happen" are unrelated to each other but I can hardly understand it.
Thanks!
A, Recently scientist learned about the changes in earth that had happened during the last ice age. wrong
B, Recently scientist learned about the changes in earth that happened during the last ice age. right
It says the two event - "learn" and " happen" are unrelated to each other but I can hardly understand it.
Thanks!


















