Why are blogs often not considered to be an authoritative source?

Why are blogs often not considered to be an authoritative source? Check all that apply.

1] They are opinion-based.

2] The authors write short entries.

3] They focus on facts.

4] The authors often lack credentials.

5] They rarely offer solutions.

THE ANSWER IS 1&4 FOR EDGEN

john maynrd keynes developed new economic respose to the                           ( b. great depression if the 1930's)