Decomposition is the process where the remains of living beings are broken down into simpler organic substances or inorganic matter.
This process is performed by the decomposers, organisms such as fungi and bacteria that feed from the organic remains.
Decomposition will occur faster in moist and warm environments, those with better conditions for each type of decomposer. On the other hand, a hostile environment such as a glacier will have fewer decomposer organisms, so the decomposition will take longer.
This means D. Glacier would be the right answer.