why the verb is past?

[Huda2]

hi,
I don't why d is best choice

the common crow,------------one of the hardiest birds in existence can live up to eighty years.
a- is considered
b- considered it
c- has been considered
d- considered
who must consider?
i feel , it make no sense with d

thanks

[Kitosdad]

Huda, your text is taken from the centre of a complete text, and this makes it difficult for you to understand, however,

who must consider ???....... the general consensus of bird watchers consider the crow to be
the hardiest of birds.
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