Answer
C.
Work Step by Step
This creates a break in the night, making the plants think that they have experienced a 10 hr day, 7 hr night, 1 sec day, and 7 hr night. Since both nights are short (plants actually look at night length, not day length), the plants think that they are in long days. B. is not specific enough to work for sure (by how much was the day shortened), and A. makes a change in the wrong direction. D. is wrong since C. is correct.
