National Significant Number Code Subdivision

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A telephone number can have a maximum of 15 digits .The first part of the telephone number is the country code (one to three digits) .The second part is the national destination code (NDC)

The last part is the subscriber number (SN)

The NDC and SN together are collectively called the national (significant) number.

According to ITU-T E.164 recommendations, the National Significant Number (NSN) is composed of the National Destination Code (NDC) and the Subscriber Number (SN). The NSN is used to identify a specific telephone number within a country or region.

The two fields in the National Significant Number code that may be further subdivided are:

1. Country Code (Option A): The country code is a mandatory field in the E.164 numbering plan, and it identifies the country where the phone number is registered. It is a fixed length of one to three digits. For some countries, the country code may be further divided into area codes, which are used to identify specific geographic regions within the country.

2. National Destination Code (Option B): The national destination code is a variable length field, which identifies the destination of the call within the national numbering plan. It can be further subdivided into regional significant numbers, which identify a specific geographic area within the country or region.

Therefore, options A and B are the correct answers. The other options, C, D, E, and F, are not part of the National Significant Number code according to ITU-T E.164 recommendations. The Subscriber Number (SN) is a variable length field that identifies a specific subscriber within the national numbering plan. The Regional Significant Number (RSN) and Local User Code (LUC) are not part of the E.164 recommendations. The National Numbering Plan (NNP) is a broader term that encompasses the entire national numbering plan, including the NSN, area codes, and other related information.