What is the correct terms to its definition?

1. A category composed of people with certain similarities, such as gender, race, religion, or even grade level. Each person belongs to only one group. A simple random sample of equal size is taken from each group. Stratum 2. A division of the population into separate physical units Population such as districts, neighborhoods, or streets. Each person belongs to only one unit. A simple random Cluster sample is taken from the units. All people within the selected units are surveyed. 3. A group of units (persons, objects, or other items) enumerated in a census or from which a sample is drawn