The concentration of urea in g per 100 cm3 in part A is 0.03, and in part C is 2.00. How many times more concentrated is the urea in part C compared with part A?

The correct answer is B.

All resources are renewable, but some of them, like the fossil fuels take so much time compared to the human lifespan, that we label them non-renewable.

For example, when you cut a tree, the same amount of wood gathered can be renewed in 20-30 years, but if you burn oil, natural gas or coal, it may take millions of years to renew the same amount used. The reason for this lays behind the name of these resources- fossil fuels. All of these resources, natural gas, coal and oil has been formed from fossilized plants and animals trough millions of years.