220-1101 Question 225
Single answerUSB-CA technician is setting up a new ultrabook that has two USB-C ports. The user reports that when a USB-C dock is connected to the left port, the laptop charges and supports an external monitor. However, when the same dock is connected to the right USB-C port, the dock's keyboard and mouse work, but the laptop does not charge and no video is displayed. Which of the following is the MOST likely explanation?
- A
The right USB-C port supports data only and does not support USB Power Delivery or DisplayPort Alt Mode
- B
The dock requires Thunderbolt, and USB-C ports can never support external displays without Thunderbolt
- C
USB-C ports are functionally identical, so the laptop motherboard must be failing intermittently
- D
The right USB-C port is limited to USB 2.0, which prevents keyboards and mice from working correctly
Show answer and explanation
Correct answer: A
Explanation
The best answer is that the two USB-C ports support different features. In A+ Core 1, candidates need to understand that USB-C refers to the physical connector, not a guaranteed set of functions. Depending on the implementation, a USB-C port may support only USB data, or it may also support USB Power Delivery (for charging), DisplayPort Alt Mode (for video), or Thunderbolt. In real-world troubleshooting, technicians should verify port symbols, check the laptop manufacturer's documentation, and confirm dock requirements. Industry best practice is to consult the system specifications because USB-C capability varies widely between systems and ports.
- A. Correct.
Correct. USB-C describes the connector shape, but the capabilities of each port can differ by device and even by port on the same laptop. A USB-C port may support only USB data, while another may also support USB Power Delivery for charging and DisplayPort Alt Mode for video output. The symptoms match this exactly: the dock's USB peripherals work on the right port, showing data connectivity, but charging and display do not.
- B. Incorrect.
Incorrect. Thunderbolt can carry video and data over a USB-C connector, but it is not the only way USB-C can support external displays. Many non-Thunderbolt USB-C ports support video through DisplayPort Alt Mode. This option reflects a common misconception that all USB-C video output requires Thunderbolt.
- C. Incorrect.
Incorrect. USB-C ports are not necessarily identical in capability. It is common for one port to support charging and video while another supports only data. Because the dock works fully on one port and partially on the other in a consistent way, differing port capabilities are much more likely than an intermittent motherboard failure.
- D. Incorrect.
Incorrect. USB 2.0 bandwidth would not explain the loss of charging and video in this scenario, and the question states that the keyboard and mouse do work from the dock on the right port. USB 2.0 is sufficient for basic input devices. The issue is the lack of non-data features, not insufficient bandwidth for peripherals.