Final Answer:
The correct order of the parts of a discrete trial is c. SD -> R <- SR.
Step-by-step explanation:
In behavior analysis, a discrete trial is a structured and controlled method for teaching new behaviors. The correct order is captured by option c: SD (discriminative stimulus) -> R (response) <- SR (reinforcement). In a discrete trial, the SD signals the opportunity for a specific behavior (R), and upon the correct performance of that behavior, reinforcement (SR) is provided. This sequence helps establish and strengthen the association between the discriminative stimulus, the response, and the reinforcing consequence.
Options a and b do not represent the accurate sequence of the discrete trial components. Option d suggests none of the provided sequences are correct, but option c accurately depicts the order of SD, R, and SR in a discrete trial.
Option C is the answer.