Which configuration summarizes external routes in the 172.16.0.0/22 range into a single prefix on an ABR for Area 1?

A.
protocols {
ospf {
area 0.0.0.1 {
nssa {
default-lsa {
default-metric 1;
metric-type 1;
}
}
area-range 172.16.0.0/22;
}
}
}

B.
protocols {
ospf {
area 0.0.0.1 {
nssa {
area-range 172.16.0.0/22;
}
}
}
}

C.
protocols {
ospf {
area 0.0.0.1 {
stub summaries;
}
}
}

D.
protocols {
ospf {
area 0.0.0.1 {
nssa;
area-range 172.16.0.0/22 restrict;
}
}
}

Explanation:
Description

(Area border routers only) For an area, summarize a range of IP addresses when sending summary link advertisements (within an area). To summarize multiple ranges, include multiple area-range statements.

For a not-so-stubby area (NSSA), summarize a range of IP addresses when sending NSSA link-state advertisements. The specified prefixes are used to aggregate external routes learned within the area when the routes are advertised to other areas. To specify multiple prefixes, include multiple area-range statements. All external routes learned within the area that do not fall into one of the prefixes are advertised individually to other areas.

Default By default, area border routers do not summarize routes being sent from one area to other areas, but rather send all routes explicitly.

Options:

exact (Optional) Summarization of a route is advertised only when an exact match is made with the configured summary range.

mask-length Number of significant bits in the network mask.

network IP address. You can specify one or more IP addresses.

override-metric metric (Optional) Override the metric for the IP address range and configure a specific metric value.

restrict (Optional) Do not advertise the configured summary. This hides all routes that are contained within the summary, effectively creating a route filter.

Range: 1 through 16,777,215