Exercise 1: Applying PICO to "Does Exercise Improve Mental Health?" — Possible Solution
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The four PICO components, made explicit:

P (Population/Problem): adults, since the original topic doesn't
specify an age group, and "improve mental health" is measured
differently across children, adults, and older adults. Choosing
"adults aged 18-64" avoids conflating three genuinely different
research populations.

I (Intervention): a specific, measurable exercise regimen - for
example, moderate-intensity aerobic exercise for at least 150 minutes
per week, matching a real, commonly used public-health threshold rather
than a vague "exercising."

C (Comparison): a sedentary lifestyle, or exercise below a defined
minimum threshold (e.g. under 30 minutes per week) - a real comparison
group is needed, since "improves" only means something relative to a
baseline.

O (Outcome): a specific, measurable mental health indicator - for
example, self-reported depressive symptoms on a standardized scale
(such as the PHQ-9), rather than the vague, unmeasurable idea of
"mental health" in general.

Assembled question: "Among adults aged 18-64, is engaging in at least
150 minutes of moderate-intensity aerobic exercise per week associated
with lower self-reported depressive symptoms (measured on a
standardized scale), compared to engaging in under 30 minutes per
week?"

ANSWER: P = adults aged 18-64; I = at least 150 minutes/week of
moderate aerobic exercise; C = under 30 minutes/week; O = self-reported
depressive symptoms on a standardized scale. Assembled: "Among adults
aged 18-64, is at least 150 minutes/week of moderate aerobic exercise
associated with lower self-reported depressive symptoms, compared to
under 30 minutes/week?"

WHY THIS WORKS AS AN ANSWER
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Each PICO component is made genuinely specific and measurable rather
than left vague, and the final assembled question could actually be
used to design a real study - directly matching what the exercise
asked for.