Answer:
Interchangeable is something that can be used in the same manner as something else without any important differences.
or in a more simple way
something that can be exchange
For example when two sweaters look almost the same and you could easily wear either one with a particular skirt, this is an example of when the sweaters can be worn interchangeably.
B. I think is the correct answer
Concaved lenses...........
my hypothesis is that If you drop a piece of buttered toast, it will land butter side down.
I tested it by dropping 10 pieces of buttered toast off the table and noted on which side it landed
It could be falsified cause I just made all of this up. In essence, it's like flipping a coin, 50/50 chance so I could say that 5 landed butter up and 5 landed butter down.