The group discussion has refined the issue, by establishing a focus i.e a device to eliminate vibration.
Option A is not correct because in this specific statement, various ideas are not being synthesized, but just a single focus is establish. Similarly option D is incorrect as there is no refuting, as the statement is not proving any claim to be false or wrong.
In option C supporting ideas with evidence may initially seem close to correct option. But when we observe the statement deeply, we come to know that there is no evidence that eliminating vibration made them successful. It is just a possibility.
