Which of the Following Are Reasons Why Workparts Must Be

Which of the following are reasons why workparts must be cleaned in industry (four best answers) :

A) to avoid air pollution
B) to avoid water pollution
C) to enhance appearance
D) to enhance mechanical properties of the surface
E) to improve hygiene conditions for workers
F) to improve surface finish
G) to prepare the surface for subsequent processing
H) to remove contaminants that might chemically attack the surface