Final answer:
In PH3, polar covalent bonds option (c) are present due to the unequal sharing of electrons between phosphorus and hydrogen, even though the molecule itself is non-polar.
Step-by-step explanation:
In the molecule PH3, the types of bonds present are polar covalent bonds. Phosphorus (P) and hydrogen (H) have different electronegativities, and in the Lewis Dot structure, the bonding electrons are shared unequally between the atoms. Since phosphorus is less electronegative than hydrogen, the electron density is greater around the hydrogen atoms, leading to a distribution of slight charges within the molecule.
However, since the molecule is symmetrical, the dipoles cancel out, making the molecule non-polar overall, but the bonds themselves are polar covalent. This differs from nonpolar covalent bonds, where electrons are shared equally, and ionic bonds, where electrons are transferred completely from one atom to another.
For example, a bond between H and C would be a slightly polar covalent bond because carbon and hydrogen have different electronegativities, with carbon being slightly more electronegative.
A bond between S and Cl would also be a polar covalent bond, and a bond between Cs and O would be a likely ionic bond due to a significant difference in electronegativity and the likely transfer of electrons.