Mojave installation
a ? is at the spot , for Mojave install choosing
MacBook Air 13", 10.14
a ? is at the spot , for Mojave install choosing
MacBook Air 13", 10.14
The "?" means your Mac cannot find a viable system to startup from.
About the screens your Mac displays as it starts up - Apple Support
Learn how to resolve a flashing "?"
Mojave installation