Which of the following describes the y-coordinates of the points on the curve e² = sin y in the xy-plane where the curve has a vertical tangent line?

a) $y = nπ$, where n is an integer
b) $y = (2n + 1)π/2$, where n is an integer
c) $y = 2nπ$, where n is an integer
d) $y = (n + 1/2)π$, where n is an integer