Which is grammatically correct? mathematics is very hard, or are? are just seems off to me. can it be used too, or is it 'is'?

imparadis't in one anothers arms  

the happier eden, shall enjoy their fill  

of bliss on bliss, while i to hell am thrust,  

where neither joy nor love, but fierce desire,  

among our other torments not the least,  

still unfulfill'd with pain of longing pines;  

yet let me not forget what i have gain'd  

from their own mouths; all is not theirs it seems:  

one fatal tree there stands of knowledge call'd,  

forbidden them to taste: knowledge forbidd'n?  

suspicious, reasonless. why should their lord  

envie them that? can it be sin to know,

this answer to this question is c. allegory

why?

stories with allegories have a hidden symbolic meaning with a theme. the hidden meaning can be political, or other real life problems.