Question: Under what conditions may the network include the Re-attempt indicator Information Element (IE) in a message?
Option 1: When the SM cause value is #20 "GPRS not allowed" or #21 "Network failure".
Option 2: When the Back-off timer value IE is included and the SM cause value is any value.
Option 3: When the network includes the APN IE and the SM cause value is #17 "unknown PDP address or PDP type".
Option 4: When the SM cause value is specific to certain PDP types (e.g., IPv4 only, IPv6 only) or when the Back-off timer value IE is included and the SM cause value is not #26 "insufficient resources".
Explanation: The network may include the Re-attempt indicator IE under specific conditions related to PDP types or when a Back-off timer value IE is present, as specified in the 3GPP TS 24.008 standard.