Why must you be careful not to touch the gold contacts at the bottom of each adapter?

Answer: You must be careful to not touch the gold contacts at the bottom of the adapter because it might damage the device

Explanation: It is advised not touch the gold contacts of the adapter because that might damage the adapter by the oils present on the fingertips of a person which leads to corrosion at times and also there are chances of damage of the electronic component by the electrostatic discharge and that leads to the failure of the device.