Which of the following is a characteristic of Players' unions in American Sports?

Once players unionize, collective bargaining must occur before league management can change hours, wages, or terms and conditions of employment

Players unions have existed since professional sports began.

Early attempts to unionize were met with general acceptance by team ownership and league commissioners worked closely with early players associations to establish their credibility.

If contract negotiations hit an impasse, players can choose to lock out the owners and thus cause a work stoppage for a professional league.

All of the above