Which Is an Example of Precarious Work

Which is an example of precarious work?

A) Window washers, who work with constant danger of falling
B) A factory worker whose fulltime job with benefits may be outsourced at any time
C) An adjunct college instructor, who is hired from semester to semester, and can lose classes a week before the term starts because of low enrollment
D) A real estate agent who depends on commission and is losing income because of the housing crisis