Elements are
a chemical substance composed of atoms of two or more different types of atoms
substances that are made up of only one type of atom
subatomic particles with a positive charge
only found on earth

substances that are made up of only one type of atom

Step-by-step explanation:

Element is a pure substance which is composed of atoms of similar elements. Example: Carbon (C)

Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.  Example: water

The subatomic particles with a positive charge are called as protons and are located in the nucleus of the atom.

Thus elements are substances that are made up of only one type of atom.

you didn't post any answer choices, so its not 100% clear what your teacher is looking for

however, log(15/7) is equivalent to log(15) - log(7)

i'm using the rule log(x/y) = log(x) - log(y)