Researchers randomly choose two groups from 15 volunteers. Over a period of 9 weeks, one group watches television before going to sleep, and the other does not. Volunteers wear monitoring devices while sleeping, and researchers record dream activity. Which type of study method is described in each situation? Group of answer choices a) observational study b) controlled experiment c) survey

B. Controlled experiment

Step-by-step explanation:

This is a controlled experiment because the variables in the question are manipulated by the researcher. We are told that while one group watches television before going to sleep, the other group does not.

The controllers won't have control over the variables that were used if it was an observational study while for a survey, it has to do with collection of information regarding certain topics or happenings in order to have people's perception on the topic or area of interest.

δabc ≅ δdcb by sas because

db ≅ ac . . given (side)

bc ≅ bc . . reflexive property (side)

∠dbc ≅ ∠ acb . . alternate interior angles where transversal bc crosses parallel lines bd and ac (included angle)

a

step-by-step explanation:

u take $30 minus $24. the answer/original($30)