Concept: The question tests on basics of Geometry 

Solution:

Since the 2 lines are parallel, ABC = BCD = 60 (Alternate angles between 2 parallel lines cut by a transversal are equal)

In triangle ECD, sum of angles of the triangle = 180

Therefore CED + 60 + 40 = 180

CED = 180 - 100 = 80

Option D