Evaluate $\sin^2\large\frac{\pi}{8}+$$\sin^2\large\frac{3\pi}{8}$$+\sin^2\large\frac{5\pi}{8}$$+\sin^2\large\frac{7\pi}{8}$

Question

$(a)\;1\qquad(b)\;2\qquad(c)\;3\qquad(d)\;4$