Meaning: 'Invented' means to create or design something that did not previously exist, in this case, emergency services.

Wrong options:

• used to happen: This phrase indicates a habitual action in the past but does not fit the context of creating something new.
• were causing: This phrase is in the past continuous tense, which does not align with the action of establishing services.
• avoided: This verb suggests evading something, which does not relate to the creation of emergency services.
• used to experience: This phrase indicates a past habit but does not pertain to the act of invention.
• liked: This verb expresses preference, which is irrelevant to the context of planning for risks.
• tried: This verb indicates an attempt, which does not fit the context of establishing emergency services.
• stopped: This verb indicates cessation, which does not relate to the act of creating something.

Correct answer: used to happen

Explanation: The phrase 'used to happen' indicates a past habitual action, fitting grammatically and contextually as it describes accidents that were common in the past.

Meaning: 'Used to happen' refers to events that occurred regularly in the past but no longer do.

Wrong options:

• invented: This verb indicates creation, which does not fit the context of describing past occurrences.
• were causing: This phrase suggests an ongoing action in the past, which does not align with the habitual nature of accidents.
• avoided: This verb suggests evasion, which does not relate to the occurrence of accidents.
• used to experience: This phrase indicates a past habit but does not specifically refer to accidents happening.
• liked: This verb expresses preference, which is irrelevant to the context of accidents occurring.
• tried: This verb indicates an attempt, which does not fit the context of accidents happening.
• stopped: This verb indicates cessation, which does not relate to the description of past accidents.

Correct answer: stopped

Explanation: The word 'stopped' is the past tense of 'stop,' which fits grammatically as it indicates a completed action. Contextually, it describes the change in how nations managed risks by the end of the last century.

Meaning: 'Stopped' means to cease or bring to an end, in this case, referring to nations no longer being able to control risks themselves.

Wrong options:

• invented: This verb indicates creation, which does not fit the context of risks ceasing to be manageable.
• used to happen: This phrase describes past occurrences, which does not relate to the cessation of risks.
• avoided: This verb suggests evasion, which does not fit the context of risks being controlled.
• used to experience: This phrase indicates a past habit but does not pertain to the management of risks.
• liked: This verb expresses preference, which is irrelevant to the context of risk management.
• tried: This verb indicates an attempt, which does not fit the context of risks ceasing to be manageable.
• were causing: This phrase suggests an ongoing action, which does not align with the idea of risks stopping.

Correct answer: were causing

Explanation: The phrase 'were causing' is in the past continuous tense, which fits grammatically as it describes an ongoing action in the past. Contextually, it indicates that the factories were continuously contributing to the damage.

Meaning: 'Were causing' means that the factories were responsible for the damage over a period of time in the past.

Wrong options:

• invented: This verb indicates creation, which does not fit the context of ongoing damage.
• used to happen: This phrase describes past occurrences but does not indicate an ongoing action.
• avoided: This verb suggests evasion, which does not relate to the factories' impact on forests.
• used to experience: This phrase indicates a past habit but does not pertain to the factories' actions.
• liked: This verb expresses preference, which is irrelevant to the context of damage caused.
• tried: This verb indicates an attempt, which does not fit the context of factories causing damage.
• stopped: This verb indicates cessation, which does not align with the ongoing nature of the damage.

Correct answer: used to experience

Explanation: The phrase 'used to experience' indicates a past habitual action, fitting grammatically and contextually as it describes the regular occurrence of hunger, illness, and disasters in the past.

Meaning: 'Used to experience' refers to events that occurred regularly in the past but no longer do.

Wrong options:

• invented: This verb indicates creation, which does not fit the context of experiencing hardships.
• used to happen: This phrase describes past occurrences but does not specifically refer to personal experiences.
• avoided: This verb suggests evasion, which does not relate to experiencing hardships.
• liked: This verb expresses preference, which is irrelevant to the context of experiencing difficulties.
• tried: This verb indicates an attempt, which does not fit the context of experiencing hardships.
• stopped: This verb indicates cessation, which does not relate to the description of past experiences.
• were causing: This phrase suggests an ongoing action, which does not align with the personal experiences of hardship.