Can't find boot into Mac OSx after updating to High Sierra. Stuck in Windows partition.
I have a MacBook air that is partitioned with most of the hard drive allocated toward Mac OS and a small amount toward Windows 10. I was updating my MacBook in Mac OS to High Sierra from Sierra. The screen went completely black during the update and then the computer turned on and opened into Windows. I can't get back to Mac OS. I have tried all the ways I know of to restart into Mac OS (Clicking restart in OSx and restarting the computer and holding down the option key). When holding down the option key after restarting the computer, there is only one option and it is the Windows partition. How do I get back into Mac OS?!?
MacBook Air, macOS Sierra (10.12.5)