upgrade macos sierra

Option keys on Mac that you don't know
the option key on the mac is rarely used until it is mistaken for not many functions. however, the option has more features than you think and they are very useful in the process of using the device.
How to fix common errors when upgrading to macOS Sierra
during the latest macos sierra version on mac, you will encounter some common errors such as not being able to open the device for use, the download file is corrupted, unable to use the application, ...