Final answer:
Methane gas is a dangerous byproduct increased by biological activity during the decomposition of organic material under anaerobic conditions. This contributes to the greenhouse effect and climate change. The correct option is B.
Step-by-step explanation:
Increased biological activity increases the production rate of methane gas which is a dangerous byproduct of organic material decomposition. When bacteria break down organic matter under anaerobic conditions, methane gas (CH4) is produced.
Such conditions are common in environments like rice paddies, the intestines of herbivores, landfills, and as organic matter decays in water-saturated areas.
Furthermore, human activities like the burning of fossil fuels and changes in land use increase the concentrations of carbon dioxide and methane in the atmosphere, contributing to the greenhouse effect and global climate change.