Which of the following statements is true? a. Pretensioning is generally done at the construction site and yields a precast, prestressed concrete member. b. Pretensioning is generally done at the precaster's plant and yields a precast, prestressed concrete member. c. Posttensioning is generally done at the construction site and yields a precast, posttensioned concrete member d. Posttensioning is generally done at the precaster's plant and yields a precast, posttensioned concrete member.