Which of the following would NOT be considered a concerted activity? Group of answer choices members of a union that meet to discuss problems with working conditions at their workplace employees who are not members of a union that meet to discuss problems with working conditions at their workplace a single employee that writes to a supervisor complaining about the refusal to grant her vacation time for the exact period of time she requested a single employee that writes to a supervisor complaining about the frequently malfunctioning air conditioning and extreme indoor heat at an assembly plant