Final answer:
The main component in the liquid form of zinc phosphate cement is phosphoric acid, which reacts with zinc oxide powder to create the cement.
Step-by-step explanation:
The main component in the liquid form of zinc phosphate cement is B) Phosphoric acid. When preparing zinc phosphate cement, phosphoric acid liquid is mixed with zinc oxide powder to initiate a chemical reaction that eventually hardens into cement. This type of cement has been widely used in dentistry as a dental cement for cast restorations and orthodontic appliances due to its strong bond, biocompatibility, and ability to withstand forces in the oral environment. The role of phosphoric acid in this reaction is crucial as it reacts with the zinc oxide to form the cement matrix.