Hydrogen bonding plays a central role in the following phenomena:
This question has multiple correct options.
A.Ice floats in water.
B.Higher Lewis basicity of primary amines than tertiary amines in aqueous solutions.
C.Formic acid is more acidic than acetic acid.
D.Dimerization of acetic acid in benzene.

Hint: We know that the ice of each water molecule is hydrogen bonded to four neighboring water molecules and forms a crystalline structure. In ice these hydrogen bonds are stable. Hydrogen bonding occurs between hydrogen and strongly electronegative atoms like Fluorine, Nitrogen, Oxygen

Complete answer:
As we know that the water is in liquid state and ice is its solid state. In solids the packing of molecules is tight as compared to liquid and gas. In water hydrogen bonding occurs as there is hydrogen as well as oxygen both are present. The formation of hydrogen bonds is an important quality of liquid water.
As hydrogen bonding occurs between water molecules, therefore it has some unique properties than other liquids. And because of these unique chemical and physical properties of water. Hydrogen atom bonds are known as the weak hydrogen bonds to elements such as chlorine and Sulphur can serve as a doner, particularly when the carbon or one of its neighbors is electronegative. It was recognized that there are many examples of hydrogen bonding with electronegativity approaching hydrogen.
These non-traditional hydrogen bonding interactions are weak bonds. These are increasingly recognized as important control elements in the receptor-ligand interaction in the science of material. The cation is more stabilized through hydrogen bonding than cation. It's a better base than in aqueous solution. Formic acid is more acidic because it has a lesser number of alkyl groups attached and hence, lesser the +I effect of alkyl groups. Acetic acid exists as a dimer because of Hydrogen bonding.

Therefore, the correct answer is option A, B and D.

Note:
Remember that it is known as a universal liquid and has a crucial role in the biological system. This type of crystalline array of hydrogen bonds leaves a space between the water molecules and these water molecules are now farther apart than they were in liquid water.