In terms of controlling chemotaxis, the proteins involved control chemotaxis in which way?

A) They control which form of flagellin is expressed.
B) They change the direction of the flagella from counterclockwise to clockwise and back.
C) They promote longer "tumbles" when a chemoattractant is present.
D) They increase the phosphorylation of CheY so that there are more counterclockwise flagella.
E) They respond to demethylation of methyl-accepting chemotaxis proteins to bring about longer runs.