Concede is to concession as announce is to

This excerpt is part of a soliloquy that reveals macbeth's inner conflictpassionate natureunscrupulous nature. he is hesitant to go ahead with the crime. the last line refers to the theme of fate versus free willappearance versus realitypower and tyranny.

But we pulled at the grill [on the ground] and it gave way. and then we saw iron rings as steps leading down a shaft into a darkness without bottom. … it was a great tunnel. its walls were hard and smooth to the touch; it felt like stone, but it was not stone. on the ground there were long thin tracks of iron, but it was not iron; it felt smooth and cold as glass. we knelt, and we crawled forward, our hand groping along the iron line to see where it would lead. but there was an unbroken night ahead. what is the most likely explanation for the walls described in the bold text?

Which factors threaten the forests of north america?