Madeline must have known the material for test because if a person knows that will get an A and was one of students got A?

The statement is flawed because correlation doesn't equal causation. Just because Madeline got an A doesn't automatically mean she *knew* the material. She could have gotten lucky, guessed correctly, or cheated. The fact that knowing the material *leads to* an A doesn't mean that getting an A *proves* she knew the material.