Describe two methods that a researcher can use to avoid obtaining a non-representative sample

One method involves taking our population and assigning every person in this population a certain number on a piece of paper. After this has been done, randomly pulling out numbers of people from the population to get a randomized sample can be done. 

Another method is stratified sampling where you proportionally divide the sample into smaller and smaller subgroups so that they are always evenly matched and representative for their subgroup - in this way you avoid having a non-representative sample.

Doulingo is good. you can also watch movies that are in french, i am using this tactic  for japanese  and it a lot. listing to music with  french  lyrics would work well too because  you could absorb  the words while having fun.hope this ! : )

What are the options?