Answer:
A. The air around you
Explanation:
The air around us is an example of matter, as it is a gas.
Air has no definite shape/volume and has no definite structure, so it is a gas.
Our thoughts aren't matter because they have no physical atoms, and radio waves and heat waves aren't matter either because they are forms of energy.
An atomic mass unit is a unit of measurement that is used to measure the mass of atoms. The atomic mass unit (abbreviated: amu or u) is roughly equal to the mass of 1 proton<span> or 1 neutron. The unified atomic mass unit and the dalton are different names for the same thing. The dalton name is used more over time.</span>
Options? I'm thinking P Waves.