Alkyl halides are almost insoluble in water because

they do not form hydrogen bonds with water

The correct answer is option 3. they do not form hydrogen bonds with water.

Alkyl halides are insoluble in water because they do not form hydrogen bonds with water molecules. Hydrogen bonds are strong intermolecular forces that occur between a hydrogen atom that is covalently bonded to a highly electronegative atom, such as oxygen or nitrogen, and a lone pair of electrons on another electronegative atom. Alkyl halides do not have any hydrogen atoms that are covalently bonded to a highly electronegative atom, so they cannot form hydrogen bonds with water molecules.

The other options are not correct.

(1) they are covalent compounds: All organic compounds are covalent compounds, so this is not the reason why alkyl halides are insoluble in water.

(2) they have low polarity: Alkyl halides are polar compounds, but they are not as polar as water. This is not the main reason why they are insoluble in water.

(4) they have tetrahedral geometry: The geometry of an alkyl halide molecule does not affect its solubility in water.

Therefore, the main reason why alkyl halides are insoluble in water is because they do not form hydrogen bonds with water molecules.