Replace the highlighted words with a single most suitable word of the same meaning from the options given below:
I couldn't prepare well for my exams as I was plagued by an unpleasant and painful headache the previous night.

Correct option is B

The correct one-word substitution is (b) excruciating.

Given expression – unpleasant and painful:
The highlighted phrase describes a headache that is both unpleasant and intensely painful — causing great suffering.

Correct answer word – Excruciating:
Excruciating means intensely painful or agonising; it perfectly captures both the unpleasant and painful nature of the headache described.
(Hindi meaning: अत्यंत पीड़ादायक / असह्य दर्द)
Example: The athlete suffered excruciating pain after the injury.

Meanings of other options:

• (a) Rapid – Moving or happening quickly (तेज / त्वरित); unrelated to pain or unpleasantness.
• (c) Disoriented – Confused about one's surroundings or situation (भ्रमित); does not describe the intensity of pain.
• (d) Ensuring – Making certain that something will happen (सुनिश्चित करना); completely unrelated to the context.