Question: What actions can a Mobile Station (MS) take when in the NO-IMSI substate?
Option 1: Perform default cell selection and initiate normal GPRS attach.
Option 2: Only perform default cell selection.
Option 3: Perform default cell selection and may initiate GPRS attach for emergency bearer services, but only in UTRAN Iu mode.
Option 4: Initiate GPRS attach without performing default cell selection.
Explanation: In the NO-IMSI substate, an MS is allowed to perform default cell selection as a basic operation. Additionally, it may initiate a GPRS attach but specifically for emergency bearer services and only when operating in UTRAN Iu mode. This ensures that even without a valid IMSI, the MS can still access emergency services under specific conditions.