You are presented with the quiz "How can diseases be trasferred?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "pathogens can cause disease" and "this suggests the pathogen may be moved through the air somehow". So, what's the best answer to the question?

Options:
(1). Getting a vaccine.
(2). By studying it.
(3). radiography.
(4). In the air.
(5). Looking at it too closely.
(6). anemia.
(7). chickenpox.
(8). influenza.
The answer is:
(4).