[BG96] When GPS+GLONASS+BeiDou+Galileo are ON which one takes precedence?

The GNSS AT command document does not mention precedence when gnssconfig enable multiple systems.
Can someone help to clarify how it works and which one takes precedence if multiple systems (e.g. GPS+GLONASS+BeiDou+Galileo) are enabled.
Also, is there a way to determine which one I am currently using?

if you enable 4 GNSS system together ,

Which satellite participates in positioning can be queried with GSA sentence,

BG96 supports joint positioning