What does task identity refer to$?$

a$.$ the degree to which a job has impact on the work of other people

b$.$ the degree to which a job requires completion of an identifiable piece of work with a visible outcome

c$.$ the degree to which a job provides independence and discretion to an individual in scheduling the work and determining the procedures to use

d$.$ the degree to which a job entails a number of different activities, requiring the use of different skills and talents