To determine the sense of shear in Figures (a) and (b), we need to understand the characteristics of S-C structures and en-echelon veins.

1. S-C Structure Analysis in Figure (a):
   • The S-plane is the schistosity or foliation plane, which forms due to deformation.
   • The C-plane, or shear plane, represents the direction of maximum shear.
   • The orientation of these planes helps in identifying the sense of shear. When the C-plane is inclined relative to the S-plane, it indicates shear sense.
   • In dextral (right-lateral) shear, the C-plane is oriented such that viewing from above, the sense of movement is clockwise.
   • In the given figure, the C-plane aligns with a dextral shear, indicating right-lateral motion.
2. En-Echelon Veins Analysis in Figure (b):
   • En-echelon veins are series of tension fractures developed due to shear stress.
   • The orientation and pattern help identify the shear sense.
   • In dextral shear, en-echelon veins typically form at an angle and show a clockwise rotation.
   • Figure (b) displays a pattern consistent with dextral shear, confirming right-lateral motion.

Thus, both figures exhibit dextral shear characteristics. This leads us to conclude the correct option is:

(a) dextral; (b) dextral