Question 18N.1.HL.TZ0.34

The diagram shows results of experiments into flowering in a species of plant.

What can be used to promote off-season flowering in long-day plants?

A.  Interrupt the day with a period of darkness.

B.  Close blinds at the end of the night to delay the start of the light period.

C.  Turn on the lights during the night for a brief period.

D.  Extend the cycle of light and dark to more than 24 hours.