Final answer:
In the equation I=prt, the independent variable is the one that can be varied freely, which is time (t), making the answer 4) t.
Step-by-step explanation:
When analyzing the formula I = prt, where I stands for interest, p represents the principal amount, r represents the rate of interest, and t represents time, it is important to understand the roles of these variables. In this formula, the independent variable is typically the one that you can change freely without being affected by the others. Since time (t) can usually be chosen or varied arbitrarily in the context of calculating interest, it is considered the independent variable in this equation. Therefore, the correct answer is 4) t.