Question: What RAT Type will an S4-SGSN send if it cannot detect that the HSPA Evolution network is behind the Iu interface?
Option 1: GERAN
Option 2: UTRAN
Option 3: HSPA Evolution
Option 4: GAN
Explanation: According to NOTE 1, if S4-SGSN cannot detect that the HSPA Evolution network is behind the Iu interface, it will send the "UTRAN" RAT Type. This is because the S4-SGSN may not be able to detect the difference between GERAN and UTRAN when GERAN Iu mode is used.