Solar energy involves electromagnetic waves and can be referred to as energy

the role of the microscope world in creating new materials .

it's all four options.

because natural gas is colorless, odorless, and tasteless, distributors add mercaptan (a chemical that smells like sulfur) to give natural gas a distinct unpleasant odor (it smells like rotten eggs). they locate the types of rock that are likely to contain natural gas deposits.