A guide dog is a dog trained to guide a blind person .However ,all dogs are colour blind .in f____,to a dog ,being colour blind isn't harmful because it has a good sense of smell .Having a good sense of smell is more i___ to a dog then being able to see colours .But you may ask ,can it get a blind person across a road s____?
Well ,dogs can be taught that they should stop when the top light ( the red light ) is lit ,and go when the b____ one ( the green light )is lit .Some dogs even don't l____ at the lights .There taught to read the traffic flow .Thus they learn to c_____the road when the triffic is s_____ .And so they can keep thir b____ masters safe .