Scientists have concluded that the uppermost part of the mantle is partially-molten. Which observation helped them reach this conclusion? Both P and S waves slow down when they reach this layer.

Both P and S waves speed up when they reach this layer.

P waves do not travel through this layer.

S waves do not travel through this layer.

Both P and S waves slow down when they reach this layer

Explanation:

The asthenosphere is the uppermost part of the mantel and is also called the magma chamber. This layer s partly molten in the state is tectonically weak and is a ductile region. It almost solid and seismic waves tend to be relatively slow through the asthenosphere. The upper-most part of the asthenosphere is believed to be of great rigidity and the brittle lithosphere.

Nonmetals usually react by gaining electrons

Yes, endothermic means it turns cold. and some chemical changes include change of tempature.