The correct option is A temperature and soil moisture
Decomposition is the process of breakdown of organic matter into simple inorganic substances. Decomposition rate is affected by:
1) Chemical composition of detritus (natural waste material like fallen leaves)
2) Climatic factors like temperature.
Temperature and soil moisture are the most important climatic factors the regulate decomposition through their effects on the activities of soil microbes. For example, warm and moist environment favour decomposition whereas low temperature and moisture inhibit decomposition resulting in build up of organic materials.