One of the primary benefits of a survey is that they A. can generate cause-and-effect conclusions
B. allow efficient gathering of unobservable phenomena
C. allow for researchers to observe one's natural behavior
D. are able to provide a detailed look at a single subject

B).  Allow efficient gathering of unobservable phenomena.

Explanation:

Surveys are described as the method of gathering information from a specified group of respondents for purposes like research or assessment of the truth of thoughts or opinions associated with a process.

As per the question, one of the most considerable benefits of the survey is that 'it allows the efficient gathering of unobservable phenomena'. The data associated with phenomena like stated preferences, behaviors, beliefs, and factual information are unobservable and can not be collected through observation but surveys help in doing so as well as in the assessment of the validity or reliability of the existing propositions about such phenomena. Thus, option B is the correct answer.

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !