#1
Heterogenous mixture mean unsimilar substances .
- Chicken noodle soyp.
- salt water
- propane.
#2
An element is a substance made of only one type of atoms
I am sorry can you explain it more?
Each isotope of Oxygen has a different number of neutrons
<h3>Further explanation
</h3>
The elements in nature have several types of isotopes
Atomic mass is the average atomic mass of all its isotopes
Isotopes are atoms has the same number of protons but has a different number of neutrons.
So Isotopes are elements that have the same Atomic Number (Proton)
Some of the isotopes of oxygen are:

Each isotope has 8 protons and 8 electrons but has a different number of neutrons
For O-16: number of neutrons = 16-8 = 8
For O-17: number of neutrons = 17-8 = 9
For O-18: number of neutrons = 18-8 = 10
Answer:
The answer is letter A. Diamond
Explanation:
The diamond is a crystalline form of carbon, with a cubic structure, of the sp³ type, that is, each carbon atom of the structure is linked to four other carbon atoms, forming a tetrahedral geometry.
nuclear fusion
Stars produce their energy through nuclear fusion. For most stars, this process is dominated by a process called the "proton-proton chain," a sequence of events that transforms four hydrogen atoms into one helium atom.