Most of the world's iron ore, including that found in northern Minnesota, formed during the middle Precambrian period, ranging in age from 1.8 to 2.5 billion years old. They are composed of alternating layers of iron-rich material, most often magnetite or
hematite, and silica. These iron oxide minerals formed on the ocean floor, creating the banded iron deposits you see here. What
was the source of the oxygen that helped to produce these deposits?
A)
The oxygen that was released into the atmosphere as a by-product of
photosynthesis caused iron deposits to oxidize creating the iron oxide
minerals.
B) Photosynthetic organisms making oxygen as a by-product of
photosynthesis and the oxygen reacted with the iron dissolved in seawater
to form iron oxide minerals.
C) The decomposition of carbon-based life forms in the oceans released
oxygen and carbon dioxide. These gases reacted with the iron deposits
forming the minerals mentioned.
D) In Earth's early biosphere, there were not organisms that underwent
aerobic cellular respiration and an excess of oxygen built up in the
atmosphere. This oxygen reacted with iron deposits to form iron oxide
minerals.

idk bring the function back   im not smart

step-by-step explanation:

1.true 2.false? ? i think. .

step-by-step explanation:

step-by-step explanation: so we look at the formula un = a + (n-1)d

un is the amount of seats

n is the nth term aka row number

a is the original sequence/row number

d is the difference between each term

so in this a=22 d=6 and n can remain as n because we are simply formjng a rule

lets put these in the equation

un=22+(n-1)(6)

this is your answer to part a

however

lets double check that this is correct, we'll try putting it into the second term

un=a+(n-1)d

u2=22+(2-1)(6)

u2=22+6

u2=28

as the question said the second row has 28 seats so now we know the formula we made is correct.

as for part b

un=a+(n-1)

its asking us to find a row with 100 seats.

remember un was the amount of seata so all we do is substitute this in.

un=100 a=22 d=6

un=a+(n-1)d

100=22+(n-1)(6)

so now we simplify to find n which is the row number.

100-22=22+(n-1)(6)-22

78=(n-1)(6)

78/6=(n-1)(6)/6

13=n-1

13+1=n-1+1

14=n

so now we know that in the 14th row there is 100 seats.

hope this and that you understood! its my first time using the app or anyone out on here : p its also me to revise so a bunch! ask more questions if you dont understand ☺

a

step-by-step explanation: