Objective has the largest depth of field.

a. High power

b. Oil immersion

c. Low power

d. Scanning

The correct answer is option - C. low power objective.

Explanation:

In microscopes, low power objectives have a wide field of view and use to study the many smaller specimens or large specimens. 10X is the power of the low objective.

To study the depth of the field the lower objective rotated and aligned on the place over the specimen. When you move to high power objective the field of view gets close in and only can study the smaller specimen or small section of a large specimen.

Thus, the correct answer is option - C. low power objectives.