#stratified-sampling

Question 1: Single choice

A university wants to estimate the fraction of its undergraduates who support a new $25 annual fee. Which of these sampling plans is NOT reasonable?

Randomly pick three ages (say 19, 20 and 23) and survey every student of those ages.1
Survey a simple random sample of 500 undergraduates.2
Group students by field of study and randomly sample 10% of the students within each field.3
Group students by year of study and randomly sample 5% of the students within each year.4