Meaning: 'Enjoyed' means to have experienced pleasure or satisfaction from something, in this case, the progress in Mathematics.

Wrong options:

• wish: 'Wish' is a verb that expresses a desire, which does not fit the context of discussing historical progress.
• failing: 'Failing' is a gerund that does not fit grammatically as it does not describe a past state of enjoyment.
• knows: 'Knows' is in the present tense, which does not align with the historical context of the sentence.
• radical: 'Radical' is an adjective and does not fit as a verb in this context.
• trump: 'Trump' is a verb that means to surpass or outdo, which does not fit the context of discussing progress in Mathematics.
• leave: 'Leave' is a verb that does not relate to the enjoyment of progress in the past.

Correct answer: failing

Explanation: The gerund 'failing' fits grammatically as it describes the ongoing action of not teaching Mathematics at school, which complements the previous clause about enjoying progress.

Meaning: 'Failing' refers to the act of not succeeding in teaching Mathematics, indicating a lack of educational effort.

Wrong options:

• enjoyed: 'Enjoyed' is a past tense verb that does not fit as it does not describe the action of teaching.
• wish: 'Wish' is a verb expressing desire, which does not fit the context of teaching or failing to teach.
• knows: 'Knows' is a present tense verb that does not relate to the action of teaching in the past.
• radical: 'Radical' is an adjective and does not fit as a verb in this context.
• trump: 'Trump' is a verb that means to surpass, which does not relate to the act of teaching or failing to teach.
• leave: 'Leave' is a verb that does not describe the action of failing to teach.

Correct answer: radical

Explanation: The adjective 'radical' describes the punchline, indicating that the conclusion drawn is significant and transformative. It fits contextually as it emphasizes the surprising nature of the observation.

Meaning: 'Radical' means relating to or affecting the fundamental nature of something; in this case, it refers to a profound conclusion about Mathematics education.

Wrong options:

• enjoyed: 'Enjoyed' is a verb and does not fit as it does not describe the nature of the punchline.
• wish: 'Wish' is a verb that does not describe the quality of the punchline.
• failing: 'Failing' is a gerund that does not fit as it does not describe the punchline's nature.
• trump: 'Trump' is a verb that does not relate to the description of a punchline.
• leave: 'Leave' is a verb that does not describe the nature of the punchline.

Correct answer: leave

Explanation: The verb 'leave' fits grammatically as it indicates an action that must occur for the punchline to make sense. It suggests that Mathematics can be better learned after exiting the school system.

Meaning: 'Leave' means to go away from a place, in this context, it refers to finishing school.

Wrong options:

• enjoyed: 'Enjoyed' is a past tense verb that does not fit as it does not indicate an action related to exiting school.
• wish: 'Wish' is a verb expressing desire and does not fit the context of leaving school.
• failing: 'Failing' is a gerund that does not relate to the action of leaving school.
• radical: 'Radical' is an adjective and does not fit as a verb in this context.
• trump: 'Trump' is a verb that does not relate to the action of leaving school.