Which of the following statements about vats used in top-down printing systems is true?

In top-down printing systems, the statement that the vats must be deep enough to contain the entire height of the part being built is accurate due to the mechanics of how these systems operate. In this type of additive manufacturing, the build platform is lowered incrementally into the vat of resin, and the print head or light source cures the resin layer by layer. For the printed part to be constructed successfully, the vat must be capable of holding the entire height of the object as it builds up from the base. If the vat is not deep enough, the component will not be fully submerged, which would disrupt the printing process and lead to incomplete or failed builds.

This requirement emphasizes the importance of the specific geometry and size of the vat in the overall functioning of top-down printing systems, making option B the correct choice. The other statements either do not reflect the necessary conditions for successful additive manufacturing or pertain to characteristics of materials and designs that are less relevant to this specific question about vat depth.