(URGENT) The diagram below shows four layers of Earth.

Which of these layers of Earth contains mainly solid iron? (100 points)

Layer A

Layer B

Layer C

Layer D

Layer A: inner core

Explanation:

The solid, inner core (Layer A) is comprised mainly of iron and nickel and is scorching hot. The outer core (Layer B) does have iron and nickel as well, but it's in its liquid form. The lower mantle (Layer C) consists of iron-rich perovskite, which is a ferromagnesian silicate mineral. The upper mantle (Layer D) is made of olivine, pyroxene, calcium oxide, and aluminum oxide.

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.

so whats the answer