In the following passage, some words have been deleted. Read the passage carefully and select the most appropriate option to fill in each blank.
Santosh Bisen, science teacher and cartoonist at Jawahar Navodaya Vidyalaya in Durg, Chhattisgarh (1) ________ his drawing (2) ________ to convert chapters into comic strips. "Convincing authorities to turn textbooks into comics was difficult. I spent my own money to (3) ________ textbooks. I also used cartoons in question papers," he says. "Students were (4) ________ with how simple science became and their performance (5) ________," he adds.

Select the most appropriate option to fill in blank number 5.

1. A
   improved
2. B
   reframed
3. C
   regained
4. D
   regretted