which fossil alone provides evidence that South America Africa India Australia and Antarctica were once joined into one supercontinent known as gondwanaland​

The fern fossil

Explanation:

The fern fossil has shaded regions in South America, Africa, India, and Australia. This provides evidence that the fern was once located on each of the four continents.

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.

the answers are a and c