In an argument, each supporting argument must be related to its parent. For example, in the argument below, "His family said he felt he was in danger from Carole" supports its parent that "There's evidence that Don feared for his life."
Use a supporting argument that is unrelated or doesn't make sense relative to its parent. In the example below, 6.b. does not make sense; a disagreement about breeding tigers isn't necessarily a reason Don feared for his life.