未知题型 8 LEDs are connected to port 2. They display by the following steps: All the LEDs are turned on for a few second All the LEDs are turned off for a few second The left 4 LEDs are turned on, while the right 4 LEDs are turned off for a few second The right 4 LEDs are turned on, while the left 4 LEDs are turned off for a few second Turn on one by one from left to right

单项选择题 关于水凝胶敷料正确的是（）

未知题型 loading and unloading is less important in logistics system which is only serviced for transportation.