Meaning: 'Develop' means to grow or acquire something over time, in this case, lifelong asthma.

Wrong options:

• needed: The word 'needed' is an adjective that implies a requirement, which does not fit the action of acquiring asthma symptoms.
• treat: The verb 'treat' implies providing medical care, which does not align with the context of developing a condition.
• released: The word 'released' is a verb that indicates an action of letting something go, which does not fit the context of acquiring asthma.
• determined: The verb 'determined' suggests a conclusion or decision, which does not fit the context of developing a health condition.
• estimated: The verb 'estimated' refers to making an approximation, which does not fit the action of developing a condition.

Correct answer: estimated

Explanation: The word 'estimated' fits grammatically as it serves as a past participle that describes the number of cases of childhood asthma. It aligns with the context of discussing statistical data regarding health issues.

Meaning: 'Estimated' means to make an approximate calculation or judgment about a quantity or value.

Wrong options:

• needed: The word 'needed' does not fit as it implies a requirement rather than a statistical assessment.
• treat: The verb 'treat' does not fit the context of estimating cases; it refers to providing medical care.
• develop: The verb 'develop' does not fit here as it implies an action of acquiring rather than estimating a number.
• released: The word 'released' does not fit as it indicates an action of letting go, which is unrelated to estimating cases.
• determined: The verb 'determined' suggests a conclusion rather than an estimation, which does not fit the context.

Correct answer: released

Explanation: The verb 'released' fits grammatically as it indicates the action of nitrogen dioxide being emitted by gas stoves. This aligns with the context of discussing pollutants associated with gas stoves.

Meaning: 'Released' means to allow something to escape or be emitted, in this case, nitrogen dioxide from gas stoves.

Wrong options:

• needed: The word 'needed' does not fit as it implies a requirement rather than an action of emission.
• treat: The verb 'treat' does not fit the context of emission; it refers to providing medical care.
• develop: The verb 'develop' does not fit here as it implies an action of acquiring rather than releasing a substance.
• estimated: The verb 'estimated' refers to making an approximation, which does not fit the action of releasing a pollutant.
• determined: The verb 'determined' suggests a conclusion rather than an action of emission, which does not fit the context.