Answer:
The explanatory variable is days of week.
Step-by-step explanation:
Regression analysis is a technique in order to check the relationship between a dependent variable (response variable) and independent variables (explanatory variables).
If we consider a regression model for example Y= mX + b
Where m is the slope , X the independent variable, Y the dependent variable and b the intercept.
An explanatory variable can be considered as the independent variable and are the variables used in order to predict the response variable Y
A response variable is the variable that we want to predict and can be considered as dependent variable or Y.
For our case we want to predict the total number of defects (response variable or dependent variable) with the day of a week (independent variable or explanatory variable)
So on this case the correct answer is:
The explanatory variable is days of week.