Question: What triggers the measurement of Successful SN terminated bearers Path Update at Secondary Node Additions in E-UTRAN?
Option 1: Receipt of an E-RAB modification confirmation message by the MN from MME when path switch is needed.
Option 2: SgNB reconfiguration complete message sent by the MN to MME.
Option 3: Inter-eNB handover or intra-eNB handover.
Option 4: SN change.
Explanation: The correct answer is Option 1 because, according to the text, the measurement is triggered on receipt of an E-RAB modification confirmation message by the MN from MME when path switch is needed. This is a specific condition that triggers the measurement, making it the most accurate choice.