---- discovery of insulin, it was not possible to treat diabetes.
A
Prior
B
The prior
C
Prior to the
D
To prior
Correct Answer: Prior to the
Prior (পূর্বে, আগে) এরপর preposition বসে, অর্থাৎ prior to something. একমাত্র option (গ) তে prior এরপর to আছে। তাই correct answer (গ)।