Answer:
D. Polar bonds and asymmetrical structure.
Explanation:
To be polar, a molecule must have polar bonds and their bond dipoles must not cancel. That is, the molecule must have an asymmetrical structure.
For example, water is a bent molecule. The O-H bonds are polar, with their bond dipoles pointing toward the O atom (See Figure 1).
The <em>x</em>-components of the dipoles cancel, but the <em>y</em>-components reinforce each other.
A. and B. <em>Wrong</em>. If the bonds are nonpolar, the molecule is nonpolar.
D. <em>Wrong</em>. If the polar bonds are arranged symmetrically, the molecule is nonpolar.
For example, carbon dioxide is a linear molecule. The C=O bonds are polar, with their bond dipoles pointing towards the O atoms (see Figure 2).
The bond dipoles are equal, but in opposite directions, so they cancel each other.
Carbon dioxide has polar bonds, but it is a nonpolar molecule because of symmetry
.