In the following passage some words have been deleted. Read the passage carefully and select the most appropriate option to fill each blank.
There is a fantastic body of evidence which indicates that (1) ________ brings down the stress chemical and it enhances (2) ________ happiness chemical. The videos of medicos (3) ________ in hospital corridors have helped us (4) ________ in these gloomy times. Indeed optimism and (5) ________ are the need of the hour.

Select the most appropriate option to fill in blank no. 2.

1. A
   one
2. B
   an
3. C
   a
4. D
   the