Astudent researcher wishes to maximize the external validity of his or her research design. what research method should you recommend to him or her?

The answer is "naturalistic observational design".

Naturalistic Observation refers to a study method that includes secretively or unmistakably watching subjects' practices in their common habitat, without intercession. Naturalistic observation is a typical research technique in conduct sciences, for example, humanism and brain research.  

This strategy is incredible on the grounds that the specialists can see the subject's conduct in their own common settings, however one noteworthy impediment is the way that it isn't generally completely clear what causes certain responses when you are managing such huge numbers of factors.

a.indigo and cochineal

b.animal hides

c.silver and gold

e.cacao beans and sugarcane