I don't know what the options were but a material that is very likely going to be challenging to recognize under a microscope as a mixture is a homogeneous mixture. A homogenous mixture is uniform and thus hard to recognize as a mixture. An example is water!
Answer:
<h2>Density = 0.00026 g/mL</h2>
Explanation:
The density of a substance can be found by using the formula
<h3>
![Density(\rho) = \frac{mass}{volume}](https://tex.z-dn.net/?f=Density%28%5Crho%29%20%3D%20%20%5Cfrac%7Bmass%7D%7Bvolume%7D%20)
</h3>
From the question
mass of air = 1.2 g
volume = 4,555 mL
Substitute the values into the above formula and solve for the density
That's
<h3>
![Density = \frac{1.2}{4555}](https://tex.z-dn.net/?f=Density%20%3D%20%20%5Cfrac%7B1.2%7D%7B4555%7D%20)
</h3>
= 0.0002634
We have the final answer as
<h3>Density = 0.00026 g/mL</h3>
Hope this helps you