I agree with your observation that in this case A was ultimately the cause of C. But as shinryuu noted above, other missions did not focus on B and did not achi

I agree with your observation that in this case A was ultimately the cause of C. But as shinryuu noted above, other missions did not focus on B and did not achieve C. Because of that, it is reasonable to conclude that something else leading to B would also lead to C. So while A was ultimately the cause of C in this case, B is the cause which matters most if you want to reproduce C, because it means you can reach C with or without A. Your statement now that B probably does not lead to C puzzles me. If that is true, then the A -> B -> C chain is broken, and your original statement that A is the cause of C (based on that chain) is invalidated. So I don't know where you are going with this.