Blockchain challenges to go mainstream in 2019

Blockchain evolution faces great challenges in the future. Please read the paper, choose
one of the challenge(s) and response to the following question(s) (but not limited to):

1. What is the challenge?
2. Why has the challenge?
3. How to solve the problems?
4. Who can solve the problems?
5. When the problem can be solved? Any road map?

Sample Solution