Meaning: 'Can' expresses the ability or possibility to do something, in this case, playing games or chatting.

Wrong options:

• cannot: 'Cannot' is the negative form of 'can' and does not fit here as the sentence is stating what children are allowed to do, not what they cannot do.
• could not: 'Could not' is the past tense negative form of 'can' and does not fit the present context of the sentence.
• were: 'Were' is a past tense verb that does not indicate ability in the present and does not fit the context of current actions.
• are not: 'Are not' is a negative present tense form that does not convey ability and contradicts the intended meaning of freedom to engage in activities.
• were not: 'Were not' is a past tense negative form that does not fit the present context of the sentence.

Correct answer: could not

Explanation: The phrase 'could not' is the past tense negative form of 'can,' indicating that young people in the past did not have the ability to stay inside all day. This aligns with the historical context of the sentence.

Meaning: 'Could not' indicates the inability to do something in the past, in this case, staying inside all day.

Wrong options:

• can: 'Can' is a present tense modal verb indicating ability, which does not fit the past context of the sentence.
• cannot: 'Cannot' is the present tense negative form and does not apply to the past situation being described.
• were: 'Were' is a past tense verb but does not convey ability or permission, making it unsuitable here.
• are not: 'Are not' is a present tense negative form that does not relate to the past context of the sentence.
• were not: 'Were not' is a past tense negative form but does not convey ability, making it incorrect in this context.

Correct answer: were

Explanation: The word 'were' is the past tense form of the verb 'to be,' which fits grammatically as it describes what children were allowed to do in the past. It maintains the past tense structure of the surrounding context.

Meaning: 'Were' indicates the past state of being, in this case, that children had permission to play outside.

Wrong options:

• can: 'Can' is a present tense modal verb that does not fit the past context of the sentence.
• cannot: 'Cannot' is the present tense negative form and does not apply to the past situation being described.
• could not: 'Could not' is a past tense negative form that does not fit as it contradicts the idea of being allowed to play.
• are not: 'Are not' is a present tense negative form that does not relate to the past context of the sentence.
• were not: 'Were not' is a past tense negative form that does not convey permission, making it incorrect in this context.

Correct answer: are not

Explanation: The phrase 'are not' is the present tense negative form of 'to be,' indicating that some adolescents currently do not have permission to engage in excessive screen time. This fits grammatically and contextually with the present tense of the sentence.

Meaning: 'Are not' indicates the current state of not being allowed to do something, in this case, staring at a screen.

Wrong options:

• can: 'Can' is a present tense modal verb indicating ability, which does not fit the negative context of the sentence.
• cannot: 'Cannot' is the present tense negative form but does not fit the structure of the sentence as it would imply a different meaning.
• could not: 'Could not' is the past tense negative form and does not apply to the present context of the sentence.
• were: 'Were' is a past tense verb that does not fit the present context of the sentence.
• were not: 'Were not' is a past tense negative form that does not fit the present context of the sentence.