Explanation

He told me that he had the duty.

Present perfect ("have") changes to past perfect ("had") in indirect speech.

Explanation

A Trap door (or backdoor) is a hidden entry point into a system that bypasses normal authentication, making it a serious security threat.

Unlike viruses or worms, it allows unauthorized access without detection, potentially exposing entire systems.

Explanation

Explanation

An algorithm is a step-by-step, well-defined list of instructions written in natural or simple language to solve a specific problem.

It serves as a blueprint for writing a program or creating a flowchart.

Explanation

Active: We do not waste time.

Passive: Time is not wasted by us.

(Subject becomes the object, and the verb is changed appropriately.)

Explanation

ISDN is a set of communication standards for simultaneous digital transmission of voice, video, and data.

It allows faster and more reliable connectivity than traditional analog systems.

Explanation

The sentence "Drive to the roundabout and then turn left" gives a command or instruction.

Sentences that give orders, directions, or requests are called imperative sentences.

Explanation

A Personal Digital Assistant (PDA) is a handheld computer used for managing personal information like contacts, calendar, and notes.

PDAs were popular before smartphones.

It often included touchscreens and stylus input.

Explanation

The rules of a programming language according to which statements are written are referred to as syntax.

Syntax defines the structure and format of valid statements in the language.

Explanation

John Dewey is known as the father of the activity-based curriculum due to his emphasis on learning by doing.

He believed education should be child-centered and connected to real-life experiences.