How does light differ from other types of waves

Embryos of different species look very similar, which shows that the organisms share a ancestor.

The alkali metals (group 1) consist of lithium (3), sodium (11), potassium (19), rubidium (37), cesium (55), and francium (87). they are soft, metallic solids with low densities and low melting points. based on the data shown in figure 1, how many valence electrons do alkali metals share?

What is the ph of a solution that has a hydrogen ion concentration of 1.0 * 10 -9 m?