Which statement about the relation between piezoelectricity and ferroelectricity is correct?

Answer: B. All ferroelectrics are piezoelectric, but some piezoelectrics, such as quartz, are not ferroelectric

Piezoelectricity is the property of developing polarization under mechanical stress and, conversely, deforming in an electric field; it requires a crystal without a center of symmetry. Ferroelectrics are crystals with a spontaneous polarization whose direction can be reversed by an electric field; they lack a center of symmetry and so are always piezoelectric. Quartz (α-quartz), by contrast, lacks a center of symmetry and is piezoelectric, but has no spontaneous polarization and so is not ferroelectric. In crystals with a center of symmetry, no first-order piezoelectric effect appears however strong the field (electrostriction, proportional to the square of the field, is a separate effect). Ferroelectric ceramics such as PZT and BaTiO₃ are poled to align the polarization before use as piezoelectric elements.