Why did alchemists sometimes use common materials like eggs and blood in their attempts to make the philosopher's stone? Group of answer choices Only organic materials were understood to be changeable; other potential materials like stone or metal were fixed. Alchemists hesitated to work other materials that might be dangerous, such as mercury. Alchemists typically could not afford more expensive materials like metals. Alchemical theory presumed that the philosopher's stone was readily available in the environment and just had to be revealed