Final answer:
The correct answer is A. 2399, which falls within the valid numeric range for extended access lists on a Cisco router (100-199, 2000-2699). Options B, C, and D are incorrect as they do not fall within this range.
Step-by-step explanation:
The student is asking about numbering for extended access lists on a router. In Cisco routers, extended access lists are identified by their numeric range. The valid ranges for extended access lists are from 100 to 199 and 2000 to 2699. According to the options given in the question and the reference numbers, option A. 2399 would signal to the router that the list should be an extended access list. Meanwhile, options B (86) and D (294) fall into the standard access list range (1-99 and 1300-1999) and option C (1375) also does not meet the given criteria for an extended access list.