Explanation
PKI stands for Public Key Infrastructure, which is a system of processes, technologies, and policies that allows you to encrypt and sign data using digital certificates1. Digital certificates are issued by Certificate Authorities (CAs) and authenticate the identity of users, devices, or services that communicate online12. Digital certificates also provide the means to encrypt and decrypt messages between sender and receiver using public and private keys2

All SFP and SFP+ optics require LC connectors so the question becomes when you need single mode fiber or multi mode fiber but the connector type is clear. SC square connectors are too big to fit in a SFP or SFP+.

Explanation
The record type that would be used to define where SIP (Session Initiation Protocol) is found is A (Address).
A record is a type of DNS (Domain Name System) record that maps a domain name to an IPv4 address. SIP is a protocol that enables voice over IP (VoIP) communication, such as voice calls or video conferencing. SIP uses domain names to identify endpoints or servers involved in a communication session. Therefore, an A record is needed to resolve the domain name of a SIP endpoint or server to its IPv4 address. References: CompTIA Network+ N10-008 Certification Study Guide, page 154; The Official CompTIA Network+ Student Guide (Exam N10-008), page 6-8.

SFP+ is a type of optical transceiver that supports 10G single-channel transmission over fiber optic cables.
SFP+ stands for small form-factor pluggable plus, and it is compatible with SFP slots on switches and routers.