Interpreters translate one command at a time during execution, as opposed to compilers and assemblers where source code for the whole application is transformed to executable code before being executed. A translator is a generic term for the others.
Source: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-
Hill/Osborne, 2002, chapter 11: Application and System Development (page 751).

Instead of using a Certificate Authority, PGP uses a "Web of Trust", where users can certify each other in a mesh model, which is best applied to smaller groups.
In cryptography, a web of trust is a concept used in PGP, GnuPG, and other OpenPGP compatible systems to establish the authenticity of the binding between a public key and its owner. Its decentralized trust model is an alternative to the centralized trust model of a public key infrastructure (PKI), which relies exclusively on a certificate authority (or a hierarchy of such). The web of trust concept was first put forth by PGP creator Phil
Zimmermann in 1992 in the manual for PGP version 2.0.
Pretty Good Privacy (PGP) is a data encryption and decryption computer program that provides cryptographic privacy and authentication for data communication. PGP is often used for signing, encrypting and decrypting texts, E-mails, files, directories and whole disk partitions to increase the security of e-mail communications. It was created by Phil
Zimmermann in 1991.
As per Shon Harris's book:
Pretty Good Privacy (PGP) was designed by Phil Zimmerman as a freeware e-mail security program and was released in 1991. It was the first widespread public key encryption program. PGP is a complete cryptosystem that uses cryptographic protection to protect e- mail and files. It can use RSA public key encryption for key management and use IDEA symmetric cipher for bulk encryption of data, although the user has the option of picking different types of algorithms for these functions. PGP can provide confidentiality by using the IDEA encryption algorithm, integrity by using the MD5 hashing algorithm, authentication by using the public key certificates, and nonrepudiation by using cryptographically signed messages. PGP initially used its own type of digital certificates rather than what is used in
PKI, but they both have similar purposes. Today PGP support X.509 V3 digital certificates.
Reference(s) used for this question:
KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten
Domains of Computer Security, John Wiley & Sons, 2001, Chapter 4: Cryptography (page
169).
Shon Harris, CISSP All in One book
https://en.wikipedia.org/wiki/Pretty_Good_Privacy
TIPTON, Hal, (ISC)2, Introduction to the CISSP Exam presentation.

Security designs should consider a layered approach to address or
protect against a specific threat or to reduce a vulnerability. For example, the use of a packet-filtering router in conjunction with an application gateway and an intrusion detection system combine to increase the work-factor an attacker must expend to successfully attack the system.
The need for layered protections is important when commercialoff-
the-shelf (COTS) products are used. The current state-of-the-art for
security quality in COTS products do not provide a high degree of protection against sophisticated attacks. It is possible to help mitigate this situation by placing several controls in levels, requiring additional
work by attackers to accomplish their goals.
Source: NIST Special Publication 800-27, Engineering Principles for Infor- mation Technology Security (A Baseline for Achieving Security).

The correct answer is "TFTP is less secure because session authentication does not occur". The Trivial File Transfer Protocol (TFTP) is considered less secure than the File Transfer Protocol (FTP) because authentication does not occur during session establishment (although FTP is very insecure in its own right).