The … of armed robbery has been on the increase.

1. Analyze the question The sentence needs a noun that means "the rate or frequency at which something occurs." The phrase "has been on the increase" tells us we are talking about how often armed robbery happens.

2. Explain the concept These words are easy to confuse:

• Incident: a single event or occurrence (e.g., "A strange incident happened yesterday.")
• Incidence: the extent or frequency of something, especially something undesirable like crime or disease (e.g., "the incidence of malaria")
• Accident: an unplanned event that causes damage or injury
• Accidence: the part of grammar that deals with word inflections. It has nothing to do with this sentence.

3. Step-by-step solution

• The sentence talks about something "on the increase," so it refers to a rate or frequency, not one event.
• Incident describes a single event, and a single event cannot "increase." The plural incidents would be needed.
• Accident does not fit armed robbery, because robbery is deliberate, not accidental.
• Accidence is a grammar term, so it is out.
• Incidence fits: "The incidence of armed robbery" means how often armed robbery occurs.

Sentence completed: "The incidence of armed robbery has been on the increase."

4. Answer The correct option is C. incidence.

5. Exam tip Remember that incidence = frequency or rate, and it is usually followed by "of" (the incidence of crime, disease, or corruption). If you can replace the word with "rate" or "frequency," then incidence is the right choice.