Which statement best describes the difference between the elastic and viscous portions of a viscoelastic tissue?

• A. Elastic portion provides immediate reversible deformation; viscous portion is time-dependent and can cause permanent deformation
• B. Elastic portion is time-dependent; viscous portion is immediate and reversible
• C. Both portions are identical in behavior
• D. Neither portion contributes to deformation

Answer: (A)

Viscoelastic tissues combine two behaviors: an elastic part and a viscous part. The elastic portion deforms immediately when a load is applied and, once the load is removed, returns to its original length—reversible and instantaneous. The viscous portion, on the other hand, responds more slowly and its deformation grows over time under sustained loading (creep). Because the viscous part can accumulate strain, some of that deformation may remain even after unloading, leading to a permanent or residual change. That blend—immediate, reversible elastic deformation plus time-dependent, potentially permanent viscous deformation—is what this statement describes best. The other options misstate the timing, reversibility, or contribution of these two components.