Ozone reaches high concentrations twelve miles above Earth, where it has long appeared that it was immune from human influence; we have now realized, though, that emissions of industrial chlorofluorocarbons deplete the ozone layer.
A) has long appeared that it was immune from
B) has long appeared to have been immune from
C) has long appeared as being immune to
D) had long appeared immune to
E) had long appeared that it was immune to
my cocncept to tense is shattered with this sc
present perfect tense is needed when an action began in past and ended in present time
past perfect is past of past
why past perfect is correct here(where is the simple past tense in this sentence)
please explain present perfect and past perfect with details
A) has long appeared that it was immune from
B) has long appeared to have been immune from
C) has long appeared as being immune to
D) had long appeared immune to
E) had long appeared that it was immune to
my cocncept to tense is shattered with this sc
present perfect tense is needed when an action began in past and ended in present time
past perfect is past of past
why past perfect is correct here(where is the simple past tense in this sentence)
please explain present perfect and past perfect with details
