"I Was Wondering Why My Houseplants Were Dying

Multiple Choice

"I was wondering why my houseplants were dying.Perhaps I was watering and fertilizing them incorrectly.Then I realized that my apartment got pretty hot when the air conditioning was off when I was away.I decided to try to find the right temperature to keep my plants healthy.For three days, I left the air conditioner set on one particular temperature, and in five-degree increments I tried temperatures from sweltering to chilly, until I finally found the temperature they liked best." This experiment used:

A) the method of agreement
B) the method of concomitant variation
C) the joint method of agreement and difference
D) a poor approximation of the method of concomitant variation