When Tobacco Plants Were Exposed to Far-Red Light,they Exhibited Increased

When tobacco plants were exposed to far-red light,they exhibited increased stem length,petiole length,and petiole angle.These three responses are part of the shade avoidance response.When the same plants were exposed to small concentrations of ethylene while being exposed to far-red light,they exhibited even greater increases in stem length,petiole length,and petiole angle.In a subsequent experiment,tobacco plants showed an increase in ethylene production in response to far-red light.Moreover,mutant plants that are insensitive to ethylene did not show a shade avoidance response when exposed to far-red light.Taken together,these data suggest that ethylene

A) inhibits growth when tobacco plants are shaded by other plants.
B) stimulates growth when tobacco plants are shaded by other plants.
C) triggers leaf abscission when tobacco plants are shaded by other plants.
D) is not involved in the shade avoidance response.