The correct answers are: You must never alter the history of the Victorian era. Time is an illusion, but lunchtime doubly so. The rookie experienced a terrifying silence when the machine broke.

Here is how articles work with abstract nouns:

• Zero Article: Used when speaking about an abstract concept in a broad, general sense (e.g., "Time is an illusion").

• The: Used when the abstract noun is specified or restricted, usually by an of-phrase or a relative clause (e.g., "The history of the Victorian era").

• A/An: Often used when an abstract noun is modified by an adjective, indicating a specific kind or instance of that concept (e.g., "a terrifying silence").