What molecules have tetrahedral arrangement of electron pairs but is not a tetrahedral molecule.

Methane

Water

Carbon dioxide

Boron trifluoride

The correct answer is Water

Explanation:

A water molecule is composed of two hydrogen atoms and one oxygen atom. Both hydrogen atoms are linked with the single oxygen atom by covalent bonding.

As oxygen atom contain 6 electrons in the valence orbital, among them 2 are used to form two covalent bond with two hydrogen atom and the rest 4 electrons are present as 2 lone pair of electrons. That"s why oxygen atom in H2O molecule is sp3 hybridized. According to the theory hybridization a sp3 hybridized molecule should have a tetrahedral arrangement.

But in in case of sp3 hybridized water molecule the tetrahedral arrangement is prevented due to priority of lone pair-lone pair repulsion.