You Buy a Schlumbergera Plant,also Known as a Christmas Cactus,to

You buy a Schlumbergera plant,also known as a Christmas Cactus,to decorate the desk where you study late into the night.It is now December,and there are no signs of flower buds forming.What is the most plausible explanation for the lack of flowers?

A) Flowering in this plant is controlled by both day length and temperature.The warm room and extended exposure to light are preventing flower formation.
B) The room is too cold for a cactus plant,which requires hot,desert conditions to flower.
C) Cacti are gymnosperms,not angiosperms,and thus do not form flowers.
D) As a long-day plant,the cactus requires a high light to dark ratio to flower,so it must be exposed to more sunlight.