CID field lengths are composed of:

• A. 1-digit event qualifier, a 3-digit event code, a 2-digit partition, and a 3-digit zone
• B. 2-digit event qualifier, a 4-digit event code, a 3-digit partition, and a 2-digit zone
• C. 1-digit event qualifier, a 2-digit event code, a 3-digit partition, and a 4-digit zone
• D. 3-digit event qualifier, a 3-digit event code, a 2-digit partition, and a 3-digit zone

Answer: (A)

The CID format uses four numeric parts in a fixed order: a one-digit event qualifier, a three-digit event code, a two-digit partition, and a three-digit zone. This structure keeps the data compact and consistent for central stations to parse quickly. The one-digit qualifier signals the broad category of the event, the three-digit code specifies the exact event type, the two-digit partition identifies the account’s partition or grouping, and the three-digit zone points to the specific zone or device involved. This exact combination—1 digit for the qualifier, 3 digits for the event code, 2 digits for the partition, and 3 digits for the zone—is why the option with those lengths is correct. Other choices mix up the digit counts in one or more parts, which would not conform to the CID standard.