**Strong Hydrogen Bond**

A strong hydrogen bond is formed between hydrogen and electronegative elements such as oxygen, nitrogen, fluorine, and chlorine. However, when considering the strength of hydrogen bonds, it is important to note that the strength of the bond decreases with increasing electronegativity.

**1. Oxygen (O)**

Oxygen is highly electronegative, and it forms strong hydrogen bonds with hydrogen. In water (H2O), which consists of oxygen and hydrogen, the hydrogen bonds between the oxygen of one water molecule and the hydrogen of a neighboring water molecule are responsible for the unique properties of water, such as its high boiling point and surface tension.

**2. Nitrogen (N)**

Nitrogen is also electronegative and can form strong hydrogen bonds. In biological molecules, such as proteins and DNA, hydrogen bonds between nitrogen and hydrogen play a crucial role in stabilizing the structure and folding of these molecules. These hydrogen bonds contribute to the overall stability and function of biological macromolecules.

**3. Chlorine (Cl)**

Chlorine is less electronegative compared to oxygen and nitrogen. While it can form hydrogen bonds, they are generally weaker than those formed with oxygen and nitrogen. However, chlorine's ability to form hydrogen bonds can still influence the physical and chemical properties of compounds that contain chlorine atoms.

**4. Fluorine (F)**

Fluorine is the most electronegative element, and it forms the strongest hydrogen bonds with hydrogen. Fluorine's high electronegativity allows it to efficiently attract and share electrons with hydrogen, resulting in a very strong hydrogen bond. This is evident in compounds such as hydrogen fluoride (HF), where the hydrogen bonding significantly affects the properties of the compound.

**Conclusion**

In summary, strong hydrogen bonds are formed between hydrogen and electronegative elements such as oxygen, nitrogen, chlorine, and fluorine. While all these elements can form hydrogen bonds, the strength of the bond varies depending on the electronegativity of the element involved. Oxygen and nitrogen form strong hydrogen bonds, while chlorine forms relatively weaker hydrogen bonds. Fluorine, being the most electronegative element, forms the strongest hydrogen bonds.

(c) F
: क्योंकि F अधिकतम electronegative होता है।