Unusually warm and humid weather conditions.
Answer: Tissue
Explanation:
Tissue is a group of similar cells that work together to serve a common function. Tissues that work together are grouped and called organs which futher makes up a system. The digestive system for instance is made of different organs such as intestine, stomach which works together to digest food.
Each digestive organ in the digestive system has its own unique tissues, with each tissue having its own unique cells.
Answer:
When burned, coal produces pollutants that are released into the air.
Explanation:
This is the only negative implication and the question mentions a 'cost' which implies a negative connotation or tradeoff when coal is used a energy source.
