Answer:
The correct answer will be-initial period.
Step-by-step explanation:
The scientific experiment contains two types of variables called: dependent and independent variables.
The independent variables are the variables in an experiment which gets changed or has to be changed to observe the effect of the dependent variable in an experiment. The independent variable has to be established in the scientific period during an initial time like time. The time is not affected by any external factor but it can control the variable to be measured.
Thus, the initial period is the correct answer.