The right option is; dark-field microscope
A light microscope that makes the specimen appear light on a dark background is called a dark field microscope.
Dark field microscopes are light microscopes that are used in different ways to clearly view various specimens that are unstained, transparent, and hard to see using a light field unit. Dark field microscopes are very effective because they show the details of unstained and live samples. It is also very simple to use, and inexpensive to set up.
This drug stops the growth of a DNA chain when added to DNA because DNA polymerase requires a 3′ end -OH group.
<h3><u>Explanation:</u></h3>
Molecular Formula: 
In a dideoxynucleoside compound the 3'-hydroxyl group attached to sugar molecules are replaced by a hydrogen. This upgrade prevents the formation of "5' to 3' phosphodiester linkages", required for the elongation of DNA chains, which results in terminating viral DNA growth.
This drug inhibits HIV replication at small level, acting as a terminator of viral DNA. The toxic side effect is "axonal degeneration" resulting in "peripheral neuropathy".
Answer:
b
Explanation:
b is the nucleus and it contains the dna