Asap !

the structural formula for butane is: ch3-ch2-ch2-ch3 which of these structures represents a correct isomer of butane?
a. ch3-ch2- ch3 ch3

b. ch3-ch- ch3 ch3

c. ch3-ch2- ch3 ch2

d. ch2-ch2- ch3 ch3

I believe the answer is A. However, I would double check the formula.

answer; economic order quantity;

geosphere and hydrosphere.

this is because the geosphere has to do with geological events, while the hydrosphere controls all water on earth.