Final answer:
The area of a circle formed by ripples at a certain time can be calculated using the formula A = πr²t.
Step-by-step explanation:
To calculate the area of a circle formed by ripples at a certain time, we need to use the formula A = πr²t. Here, r represents the radius of the circle and t represents the time in seconds. So the correct equation to calculate the area is A = πr²t, as mentioned in option B.