In which of the following cases could you use a paired t-test? When comparing the proportions of smokers between a group

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In which of the following cases could you use a pairedt-test?
When comparing the proportions of smokers between a group ofmales aged 30 to 39 and a group of males aged 40 to49.
When comparing the mean BMI of subjects before and afterparticipating in an exercise program.
When testing if the odds of smoking differs by race/ethnicitygroups.
When comparing the survival curves between two groups ofpatients who developed myocardial infarction (MI) over a period of10 years.