Concept:"Chalk" is an uncountable noun, so it needs a quantifier like "some", not plural or article forms used with countable nouns.Explanation:The complete sentence is: "The teacher needs ... to write the note on the chalkboard."Because chalk is a material (uncountable), we cannot say "chalks", "a chalk", or "many chalks".The correct way to express an indefinite amount is "some chalk".Thus, the best option is C.Answer:C. some chalk