Answer:
The two structures most likely to be observed by the scientist when looking at a type of bacteria under the microscope are cell wall and vacuole (option C).
Step-by-step explanation:
Bacteria are prokaryotic organisms that lack a nucleus, most of the organelles, and whose DNA is dispersed in the cytoplasm. Some types of bacteria have a plasma membrane surrounded by a cell wall, and may be equipped with vacuoles to perform their functions.
It is very likely that two structures that are most likely to be differentiated when a type of bacteria is observed under the microscope are the cell wall and the vacuole, according with information above.
The other options are not correct because:
A and D. Bacteria lack a nucleus.
A and B. Bacterial DNA is dispersed in the cytoplasm and is very difficult to observe under the microscope.