Unable to locate adb

#1

My android studio was working fine bt all of a sudden it is showing error
11:59 PM Unable to detect adb version, adb output:
plz help how to fix it.

#2

go through all the stack overflow links on the google result page

https://www.google.com/search?q=Unable+to+detect+adb+version%2C+adb+output%3A&rlz=1C5CHFA_enIN852IN852&oq=Unable+to+detect+adb+version%2C+adb+output%3A&aqs=chrome..69i57j0l5.443j0j7&sourceid=chrome&ie=UTF-8