In a crosstabulation
a. either or both variables can be categorical or quantitative.
b. both variables must be quantitative.
c. one variable must be categorical and the other must be quantitative.
d. both variables must be categorical.

D - both variables must be categorical

Explanation: Crosstabulation is a technique used in the examination of 2 categorical variables. It is also known as contingency table analysis.

Crosstabulation is an analytic and useful tool in marketing research.

It creates a good relationship between the variables with its unique naming. its variables have a low chance of standing alone.

the u.s. census bureau produces data on the population and economy nationwide. it can you to analyze the kind of people living in your neighborhood. it does not show you the market of people willing to buy your product or an existing market for your product. that will require more market research. the census bureau only gives you an insight to the demographics in your area.

b. take periodic breaks and alternate between tasks.  

will increase work efficiency, and avoid health issues.