After Setting the Correct Photoperiod, the Managers of a Greenhouse

After setting the correct photoperiod, the managers of a greenhouse still do not have blooming roses. Which of the following possibilities would most likely have contributed to the problem?

A) The heating system allowed for fluctuations in temperature between 20°C and 25°C.
B) The furnace mechanic accidentally turned off the lights for an hour two days in a row.
C) The cleaning crew turned the lights on for an hour three nights in a row.
D) All of the above
E) None of the above