A、The survey needs more than 4,000 people. B、A minority of people never clean the keypad and the mouse. C、10 people never clean

M: Hi, Jenny, why are you still eating while you are using the computer?
W: Why? I don’t make the keypad dirty.
M: Think twice before eating those dropped crumbs off your computer keyboard — you might as well be eating off a toilet seat.
W: That’s horrible: I don’t believe that at all.
M: A study by British Consumer magazine who asked a microbiologist to examine for bugs on 33 keyboards in a typical London office, a toilet seat and a toilet door handle.
W: What’s the result? Is it serious?
M: Yes, four keyboards were judged potential health hazards and the microbiologist recommended the removal of one keyboard as it had five times bacteria than the cleaned toilet seat.
W: Most people don’t give much thought to the dust and dirt that builds up on their PC.
M: But if you don’t clean your computer, you might as well eat your lunch off the toilet.
W: Does it mean that dropped crumbs and food encourages the grows of millions of bacteria?
M: Sure, the study found that eating at computer desks is the main cause of bug-infected keyboard.
W: In that way, poor personal hygiene, such as not washing hands after going to the toilet, may also add to the dirtiness of the keyboards.
M: But as far as I know, a survey of 4,000 people by the magazine found one in ten people never cleaned their keyboards while another two in ten never cleaned their mouse.
W: Oh, I should first clean my hands and learn how to clear out bugs.
Questions 12 to 15 are based on the conversation you have just heard.
12. Why is the woman advised not to eat at the computer?
13. What can we know about the microbiologist’s examination?
14. Which is the cause of a bug-infected keyboard?
15. What can be inferred from the conversation?