Explanation:

Explain 
Checking A-F:
RBI in its third Bi-monthly Monetary Policy review has reduced its key policy rate by an unorthodox 35 basis points.
The above sentence is correct both grammatically and contextually.
Checking B-D:
Paraphrasing is all well and good as long as you don't have the original sentence in sight when you seek to paraphrase.
The above sentence is correct both grammatically and contextually as well.
Checking C-E:
They arrived early so as to get really good seats.
The above sentence too is correct both grammatically and contextually.
Option B is hence the correct answer.