Which of the following languages is regular?

a$.\{w{w}^R|win\{0,1{\}}^{**}\}$

b$.\{w{w}^{R}x|w,$xin$\{0,1{\}}^{**}\}$

c$.\{xw{w}^R|w,$xin$\{0,1{\}}^{**}\}$

d$.\{wx{w}^R|w,$xin$\{0,1{\}}^{**}\}$