听力原文： Can this bird help alleviate the pain caused by some common ailments? Well, its bite certainly won't help matters, but its oil just might. Emu oil, a legendary treatment first used by Australian aborigines hundreds of years ago, is produced by rendering fats from the bird. The aborigines used it to treat their wounds. Today, this folklore remedy is getting new attention from scientists. A team of researchers from Australia's Adelaide Women's and Children's Hospital is trying to find out, once and for all, if the flightless bird truly possesses healing powers, and they've been encouraged by previous tests that have demonstrated the oil's value, especially in the treatment of arthritis. Should be always careful and should be armed with technical know-how to lay bare the lies in ads. Otherwise any credulity will lead to financial and spiritual losses. Secondly, ads are a waste of time, for they wantonly interfere our recreational time without our agreement, which is especially unbearable when the fussy commercials repeatedly interrupt the exciting TV serials and programs. Last but not least, ads are a sort of pollution of both eyes and ears. Some people hold the view that the ads covering the walls and buses actually enrich the living environment. But I can't help asking that why not a colorful painting instead of an ad on a blank wall which certainly will make this bustling world appear purer and more beautiful. Without ads, we will find the world pleasing to both the eye and the mind. I understand that ads have made positive contributions to modern economic development. However, if their creditability is out of control, I think that it's not only a tragedy of ads but also of modern civilization. What is the passage primarily concerned with?