Each entry in a(n) database has one parent node, with the parent node having several child nodes.

The correct answer is - hierarchical

Each entry in a(n) hierarchical database has one parent node, with the parent node having several child nodes.

A hierarchical database model is a data model where the data is organized into a tree like structure. The data is stored as records and these are connected to one another through links.

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.

when the displaced particles are perpendicular to the direction the wave travels, is called a transverse wave, whereas in longitudinal wave the displace practices are parallel to the direction of the wave.

in the given image:

first image shows - longitudinal wave

second image shows - transverse wave

third image shows - longitudinal wave

fourth image shows - longitudinal wave