1. which of the following best describes an example of pure chemistry?
a) testing the effects of lower concentrations of a drug on humans
b) studying chemicals containing carbon
c) developing a cure for osteoporosis
d) finding an antidote for a new strain of virus

2. which of the following can be observed only in a microscopic view?
a) foam insulation
b) x-ray of a knee joint
c) shape of a soybean plant
d) structure of a muscle cell

3. the variable that is observed during an experiment is called what type of variable?
a) independent
b) manipulated
c) controlling
d) responding

Q1. The answer is b) studying chemicals containing carbon.
Pure chemistry, as its name suggests, is the study of pure, basic theory of chemistry, and has no applied aspect. On the other hand, there is applied chemistry with research for some intended purpose and application. Now let's take a look at the choices: effects of drugs on human (purpose is understanding drug effects), a cure for osteoporosis (applied aspect), an antidote for a new strain of virus (applied aspect) are examples of applied chemistry because they have some purpose. On the other hand, studying chemicals containing carbon has no applied aspect, it is a study because of pure knowledge.

Q2. The answer is d) structure of a muscle cell.
Among choices, only the structure of a muscle cell is not visible to human eyes. Imagine foam insulation, X-ray of a knee joint, a shape of a plant -  all of these are visible to human eyes. However, if you want to see a structure of a muscle cell, you will need a microscope. The microscopes are able to magnify specimens and are used to see structures that you cannot see with naked eye.

Q3. The answer is d) responding.

An independent (manipulated) variable is variable that is not affected during the experiment. It is what experimenter controls.  A responding variable is also called a dependent variable. The dependent (responding) variable is called dependent because it depends (it responds) on the independent variables. It is what is affected and what is observed during the experiment.