REVIEW QUESTIONSselect the one correct response for each of the following multiple-choice questions.1. Porcelain restorations havea. Great stain resistanceb. Low wear resistance c No disadvantagesd. Easy reparability2. Porcelain bonds to metal by which one of the following mechanisms?Ca. Micromechanical retention such as resin to etched enamelb. Penetration through the surface of the metalc. Fusion with axides on the surface of the metald. Shrinkage when fired so that it lods onto the metal3. The main advantage of all-ceramic crowns over porcelain-bonded-to-metal crowns isaa. Their superior estheticsb. Their strengthTheir ease of cementationd. The ease of taking shades