正解:C
A SQL server connects over port 1433. Port numbers are used to identify specific applications or services on a network device. Port 1433 is the default port for Microsoft SQL Server, which is a relational database management system that uses SQL (Structured Query Language) to store and manipulate data. References: CompTIA Network+ N10-008 Certification Study Guide, page 147; The Official CompTIA Network+ Student Guide (Exam N10-008), page 6-4.