Which is the best description of the chemical reaction shown here in aqueous solution? ch3ch2cooh (aq) ↔ ch3ch2coo- (aq) + h+ (aq)?

The given reaction: 
ch3ch2cooh (aq) ↔ ch3ch2coo- (aq) + h+ (aq)
is called a reversible reaction.

This means that, the reaction does not reach an end point.
In this type of reactions, reactants react together to form products, while products combine together to form reactants.
So, the reaction proceeds in both direction forming both reactants and products.

The use of piers and beams to build a strong foundation for a house.

B. a graduated substance