What does the phrase"impose duties" refer to?

Imposed duties are duties, the burden of which is imposed upon a person. They are those duties of a municipal corporation which are superadded to merely governmental functions, like the special private corporate duty to maintain streets in a safe condition for public travel, or the special, private corporate duty to maintain and manage corporate property so that city employees shall have safe places in which to work.

d is the answer. leo should include the source.

north atlantic treaty organization.