You can use two active and two passive adapters. It also all depends on the resolution you are using. Lets say that you have displays that go above 1200p, then you will need active adapters.
Viewsonic V3D231 both are 1080p (you can use two passive miniDP to HDMI™)
acer AL1716 d-sub.DVI (here you can use active adapters)
LG 16M65A I cannot find information but you can use here active adapters just in case.