Please choose the correct solution to the question: To charge the battery of a smartphone,

Solution1: you should plug a USB cable in a power supply, plug the supply in an outlet, plug the cable into the wireless charging pad and lay the phone on it.

Solution2: you should plug a USB cable in a power supply, plug the supply in an extension cord, and plug the other end of the USB cable directly into the phone.

Answer format: solution1/solution2
Answer: solution1