He was uncertain _____ which road to take.

Complete sentence: He was uncertain as to which road to take.

• As to
English Meaning: about.
Bangla Meaning: সম্বন্ধে।
Ex. Sentence: There's no decision as to when the work might start.
Bangla Meaning: কাজ কখন শুরু হবে সে ব্যাপারে এখন কোন সিদ্ধান্ত হয় নি।

Options,
ক) as in:
- In the sense of/ It is commonly used to mean "which is..." or "which means..."

গ) as if:
- used to say that you doubt something very much.

ঘ) as of:
- starting from a particular time.

Source: Website Lecture.