After it has been tested and verified.
True because of supply and demand. If the demand is higher than the supply, or people cannot afford the supply, the demand must decrease in value so that people can facilitate the supply and keep it going.
They created the valleys because they pulled them downstream
Answer:
Bellows
Explanation:
A bellow or pair of bellows is a device constructed to furnish a strong blast of air. The simplest type consists of a flexible bag comprising a pair of rigid boards with handles joined by flexible leather sides enclosing an approximately airtight cavity which can be expanded and contracted by operating the handles, and fitted with a valve allowing air to fill the cavity when expanded, and with a tube through which the air is forced out in a stream when the cavity is compressed
