Answer:
(c). Random Stratified
Step-by-step explanation:
Sampling refers to selection of a number of observations for analysis as a representative of the entire population of observations wherein the results would be interpreted the same as if the whole population was subject to analysis.
In a stratified random sampling, the observations are divided into small groups known as strata which relate to a sample interval, from which an item is chosen at random.
In stratified sampling, the selection of an item is taken from the observations belonging to a strata belonging to a particular sample interval.
In the given case, stratified random sampling has been used.