Select all that apply.

which of the following statements best describes a characteristic of an observational study?

the researcher imposes, for example, a treatment on the sample population and then observes their response.
the researcher determines relationships among variables.
the individuals are observed the exact way they act in real life.
it is the best method to learn about cause-effect relationships.

The individuals are observed the exact way they act in real life.

Step-by-step explanation:

There are two main types of studies in research; one is controlled or experimental and the other is observational.

In observational studies, the individuals participating in study are not manipulated or intervened or controlled in any way by the researcher.

Hence the statements best describes a characteristic of an observational study is the individuals are observed the exact way they act in real life !

option (b) is correct

step-by-step explanation:

to find the solution of this system, we need to convert it into reduced row-echelon form. we have,

after applying row operations r2 -> r2/2 and r3 -> r3/3, we get,