$2-$Which of the following statements is true of the transactional model of communication? $($a$)$ It underscores the simultaneous sending and receiving of messages in a communication episode. $($b$)$ It illustrates that a person can perform the role of either sender or receiver during an interaction, but not both roles simultaneously. $($c$)$ It suggests that a person is only a sender or a receiver in a communication episode. $($d$)$ It suggests that the roles of the sender and the receiver are independent in the effectiveness of communication.