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.

frequency, z, and the collision density, z, in carbon dioxide (co2), r 180 pm at 30 °c and 120 kpa