Which product is negative?

___________________________

a) −3⋅(−2)⋅(−4)⋅(−7)


b) −6⋅(−7)⋅(−8)⋅0


c) −2⋅(−7)⋅12⋅(4)


d) 4⋅(−9)⋅(−3)⋅(−1)