Motile Bacteria Have Been Placed in an Environment with a Gradient

Short Answer

Motile bacteria have been placed in an environment with a gradient of a chemical attractant.Which of the following behaviors would you predict?
A.Bacteria will randomly switch back and forth between runs and tumbles.
B.The bacteria will only exhibit runs away from the chemical.
C.The bacteria will reduce tumbling frequency.
D.The bacteria will reduce run duration in the direction of the chemical.
E.The bacteria will both reduce tumbling frequency and increase run duration in the direction of the chemical.