Institution: জাতীয় কবি কাজী নজরুল ইসলাম বিশ্ববিদ্যালয় (JKKNIU) Exam: গ ইউনিট || জাতীয় কবি কাজী নজরুল ইসলাম বিশ্ববিদ্যালয় || 2012
Topic: Sentence (বাক্য), Subject: English Grammar (ইংরেজি গ্রামার)

Best Answer Explained in Below-:

The correct noun form of "sure" is "sureness." Understanding this can be achieved by analyzing each provided option.

1. **Surety (A)** refers to the state of being sure or certain but often implies a legal or financial guarantee. While it is derived from "sure," it does not directly represent the noun form of the quality of being sure.

2. **Sure (B)** is an adjective that describes a state of confidence or certainty. It cannot function as a noun on its own.

3. **Surely (C)** is an adverb that expresses certainty and is used to reinforce the truth of a statement or assertion. Like "sure," it doesn't serve as a noun.

4. **Sureness (D)**, on the other hand, directly encapsulates the quality or condition of being sure. It captures the essence of assurance and certainty, which aligns perfectly with the noun form derived from the adjective "sure."

Thus, "sureness" is the only option that accurately represents the noun form of "sure," making it the correct answer.