Play 30 minutes with each class online in Exo Survival.

There are a total of three classes to choose from in Exo Survival, these are as follows:

Light Exo - Fastest movement speed, full range of boost abilities, lowest Armor. SMGs and Assault Rifles. UAV class Scorestreak.
Heavy Exo - Slowest movement, limited boost abilities, highest Armor. High Damage, heavy weapons. Goliath Scorestreak.
Specialist Exo - Normal Movement, limited boost abilities, normal Armor, Shotguns and Sniper Rifles. Sentry Gun class Scorestreak.

You need to play for 30 mins with each one. There is no way to check this, but most games last around an hour (It tells you at the end on the scoreboard screen how long the game lasted for). Also, this needs to be done in either public or private online modes. Playing Local Play won't count towards the 30 minutes on any of the classes.