Answer:
C. the boiling point of water
Explanation:
B is correct because boiling point only usually differs among the same substance when pressure changes. So say you take one solution onto a mountain top and another at sea level, the boiling point will not be the same, but here we assume they are in the same place so it won't.
A cannot be because the containers are all different shapes (and we aren't talking about like molecular shape of water from what I assume, we mean macroscopically, so that can't be).
B cannot be because we have 4 different temperatures.
D cannot be because we have 4 different temperatures, and therefore different amounts of steam will be released per minute as not all the waters have reached boiling.
