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Let d c N, a E Z, b E Z so that d = max {c E N; (cla A c b) }. What do you call d. Select one: O a. dis coprime to a and b. O b. d is the greatest prime number lower than a or b. O c. d is the greatest common divisor of a and b. O d. d is the smallest common multiple of a and b. O e. d is not a number because it would be divided by zero.When is a connected graph called planar? Select one: C) a. When edges cross each other, no matter how you draw it. C) b. A connected graph is always planar. c. When there is an odd number of vertices. I) d. When it has a cycle. 9. When it can be drawn so the edges don't cross each other