Which supercontinents were present on earth at the beginning of the crustaceous period? a. Rodinia
b. Pangaea
c. Laurussia and Gondwana
d. Laurasia and Gondwana

The supercontinent that was present at the beginning of the Cretaceous was Laurasia and Gondwana (option d).

Explanation:

The Cretaceous period was preceded by the Jurassic and followed by the Paleocene, being a division of the Mesozoic era.

Laurasia and Gondwana were the result of the division of the supercontinent Pangea at the beginning of the Cretaceous period. Laurasia was predominantly located to the north, while Gondwana was to the south, which gave way to the continents known today.

The other options are not correct because:

    a. Rodinia existed in the Proterozoic.

b. From Pangea Laurasia and Gondwana were formed.

c. Laurussia is another name for Laurasia

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.