What does a chemical equation describe ?

A chemical equation describes the before and after of a chemical reaction.

It shows . . .

-- what substances are present before the reaction starts

-- how much of each

-- what substances are present after the reaction ends

-- how much of each.

it is the second option.

there is no correct list among the choices you've provided.

the list might look something like this:

-- baby human

-- piccolo

-- flute

-- soprano singer

-- trumpet

-- tenor singer

-- trombone

-- baritone singer

-- baritone horn

-- bass singer

-- tuba

since i had to make up the list myself, i made it easy on myself, and i didn't try to shuffle the string instruments and woodwinds into it too.