Pick up the correct statement from the following?

A. if the float is positive and the activity is delayed by a period equal to its total float, the completion of project in not delayed

B. if the float of an activity is negative, delay in its performance is bound to delay the completion of project

C. the float may be positive, zero or negative

D. if the float of an activity is zero, the activity is critical and any delay in its performance will delay the whole project