Which of the following is an example of a longitudinal wave? O A. A wave of ocean water as it reaches the beach.
O B. A wave on the surface of a drum that has been struck.
O c. A wave traveling down a long, stretched string, with both ends held
fixed.
OD. A wave traveling down a stretched Slinky toy, with both ends held
fixed.

A. they hold atoms  together with a molecule.its a force that exist between molecules. hope this .

Answer;

hot magma rises and pushes up toward the lithosphere, and as it cools it cycles back down toward the core to be heated again.

explanation; convection currents are the circular pathways taken by a fluid that enhances heat transfer by the process known as convection which occurs in fluids.convection currents transfer heat from one place to another by mass motion of a fluid. earth mantle is in a semi-liquid state and behaves like any other fluid, rising up from the bottom of the mantle after becoming hotter and less dense from heat of the earth's core, as the rock loses heat into the earth's crust it becomes cooler and more dense, then sinking back down to the core, then repeating the cycle.