Final answer:
The correct command to turn the turtle right by 90 degrees in a Turtle graphics program is turtle.right(90). This rotates the turtle to the right by the given angle.
Step-by-step explanation:
The command to turn the turtle right 90 degrees in a Turtle graphics program is turtle.right(90). This method is used to rotate the turtle (which represents the cursor or pen) to the right through the specified angle, which is 90 degrees in this case. This command is part of the Turtle module in Python, commonly used for introducing programming concepts to beginners.