What do these characteristics all have in common?

(Characteristics in the picture)

They are all dominant.
They can all be easily observed.
They are all recessive.
They can all be applied to other plants.

They can all be easily observed.

Explanation:

One distinguishing feature that Gregor Mendel watched out for in Garden peas was that all characters were easily observed.

Thus, he could easily differentiate between wrinkle and smooth peas, tall and short pea plants, purple-color seed and yellow-colored seeds etc, all because they the traits could be easily observed

A. to modify the density of materials present on Earth

Explanation:

The significance of the collision of dust, ice and the rocks and other matter with the earth was to change and modify the climate and density of the matter present on the earth. As this collision creates massive changes in the earth geologic formations and lithosphere and owning to this collision has led to what is knows as the present earth's characteristics.