Final answer:
The syntax (9)A refers to connecting the control wire to digital pin 9 on a microcontroller or similar device, commonly used in digital electronics like Arduino. Thus option D is correct.
Step-by-step explanation:
In electronics manuals, the syntax (9)A conventionally denotes a procedural step, commonly found in guides for wiring or device configuration. Specifically, it instructs users to establish a connection by linking the control wire to digital pin 9 on a microcontroller or a comparable device. This format adheres to a widespread practice in electronics documentation, where parenthetical numbers alongside letters typically signify pin numbers on a given device.
Such instructions are particularly prevalent in the programming of digital electronics platforms like Arduino or Raspberry Pi, where the manipulation of pin behavior occurs through code. This standardized notation streamlines the process for users, facilitating a seamless integration of hardware and software in the realm of digital electronics. Aspiring electronic enthusiasts and developers often encounter this syntax, finding clarity and precision in its application for effective and error-free circuit implementation.