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!
N=6.98*10²⁴
Nₐ=6.022*10²³ mol⁻¹
n(Mg)=N/Nₐ
m(Mg)=n(Mg)M(Mg)=M(Mg)N/Nₐ
m(Mg)=24.3g/mol*6.98*10²⁴/(6.022*10²³mol⁻¹)=281.7 g
Answer: Yes
Explanation: Plasmids offer a number of unique characteristics that make genetic engineering much more efficient. Plasmids are a type of non-chromosomal DNA. Integrating DNA into a bacterial or other chromosome is far more complex than simply putting DNA into a cell; plasmids make it easier to transport DNA into a cell by eliminating this step.