Misc: Who is Krusty's secretary??

Questions

Term indicating the hydrogen ion concentration of a solution, a measure of the solutions acidity?

Term meaning `rest' which titled a posthumous RAH retrospective?

Term originally meaning any kind of bird, & later applied chiefly to edible species?

Term popularly applied to a visible growth of fungi or bacteria on wet clothes, food, or other objects?

Term used to designate a crew member for manned space flights of the united states space program?