Agraph of coal reserves in the united states versus time slopes downward this indicates that coal production could have
decreased
increased
fluctuated
stayed the same

Option A.

Explanation:

It is given that a graph of coal reserves in the united states versus time slopes downward.

It means, in the graph x-axis represents the time and y-axis represents the coal reserves.

Negative slope represents the negative relation between coal reserves and time. It means coal reserves will decrease if time increases.

In other words, the downward slope indicates that coal production could have decreased.

Therefore, the correct option is A.

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.