Final answer:
The amount of wire needed to solder a circle in a stained glass window corresponds to the circumference of the circle, calculated by the formula 2πr.
Step-by-step explanation:
The question pertains to finding the amount of wire needed to solder the circle in a stained glass window. To determine this, we must find the perimeter of the circle which is given by the formula circumference = 2πr, where r is the radius of the circle. Substituting the wire for the circle's perimeter, we can conclude that the amount of wire needed to solder the circle is represented by the length of the circumference. Therefore, the correct answer is option (a) 2πr.