Select the most appropriate option that can substitute the highlighted segment in the given sentence.
After a long journey I was looking forward to sleep on a comfortable bed.

Correct option is A

The correct substitution of the highlighted words is (a) sleeping in a.
Explanation: After look forward to, the to is a preposition; therefore it must be followed by a gerund (V-ing), not the base verb. Hence, looking forward to sleeping is correct. Also, the natural collocation is sleep in a bed, not sleep on a bed in this context of normal rest. (Hindi: look forward to के बाद V-ing आता है; “bed” के साथ सामान्यतः sleep in a bed प्रयोग होता है.)
Grammatical rule used: Prepositions (including to in phrasal-prepositional verbs like look forward to) take gerunds: be used to doing, object to going, commit to improving.
Example: She is looking forward to meeting her grandparents.
Information booster: Compare: want to + V1 (infinitive) vs look forward to + V-ing (gerund). Different to, different complements.