Which best describes the nucleus of an atom
a. it is the negatively charged part of the atom.
b. it is the most passive part of the atom
c. it is made of neutrons and electrons.
d. it contains no mass.

What was the land like over 500 million years ago? what was under the sea?

What is the difference between an igneous, sedimentary and metamorphic rock

Food webs - transferring energy and matter from one level to another. here you see four food webs. one or more are incorrect. which food web(s) show the correct sequence of organisms, from start to top level consumer? a) a b) d c) c d) a and d