The answer is D. They already knew about animals, plants and skin.
Answer is 6.84 approx
reason:-
(2.78^2+6.25^2)^1/2=6.84 approx
To find the answer, plot down the factors for every number.
12: 1, 2 ,3 ,4, 6, 12
18: 1, 2, 3, 6, 9, 18
84: 1, 2, 3, 4, 6, 7, 12
If you noticed, the number that was common to the 3 numbers, were 1, 2, 3, and 6
And 6 is the bigger number
So 6 is your GCF
Rate of performing work is called power.
Time = work done/Power = 1800/300 = 6 sec.
Therefore it takes 6 secs to perform work.
.....When astronomers developed ways to measure distances, they could plot, this angle from north, this many light years, so relative to us that star is here. Plot many stars this way and you will see the shape of the galaxy.... i think this is a response right?