What is the difference between the time avail-to do a job and the time required to do the job known as?

Option "B" float could be considered the best among the available options. 

float or slack is the amount of time that a task in a project network can be delayed without causing a delay , so I think B

This principle is developed by Frederick Taylor since 1911 is to determine the time to do the work on the basis of average worker after removing unnecessary movements and train workers perfected less time

Option "B" Float will be the correct answer of your question.

I leave the answer of professionals, thanks for the invitation. 

my choice is Option "B" float

B. float...sometimes called slack, is the amount of time a project can be delayed from early start without changing the completion date. 

thanks for invition ,,,,,,,,,,

my choice is option C

Thanks invite. ........... l think event 

I think float is the answer

Difference between time available to do a job and time required to do a job is float. If more time is available, float is positive and if less time is avalable than required, float is negative.