The answer to the question is (A.)
The pH of an amino acid is determined by the nature of the side chains of that amino acid. If the side chain of an amino acid contains amine functional group the amino acid will be basic. The acidic amino acids are acidic because they have carboxylic acid functional groups at their side chain.
The property that makes slate most suitable for roofing shingles is that it can be split into thin, flat layers.
This means that the roofs of houses and other buildings can be created from slate in order to cover the tops in the best way possible. Other materials are also often used for this purpose, but slate is one of the most popular ones nowadays because of that property it has.