Reporter: I am representing China Daily. I am from the 21st century China, an east country in Asia. I am here to interview you for more information to write my feature article about you. John Snow: You are welcome. I know of China. It is a great country. Yes, I'm John Snow, a London physician. I lived and worked in the mid-nineteenth century as an obstetrician. I was among the first to use anesthesia. Reporter: During the 1830s and 1840s, when severe cholera epidemics threatened London, how did you become interested in the cause and transmission of the disease? John Snow:... Reporter:... 2. Learning about the making and uses of past participle

To form the past participle of a verb, add the ending -ed to the base form. (But note that many common verbs have irregular past participle forms.)

　　The past participle is used in the following circumstances

◆After the auxiliary have in the perfect tense

Has the radio been fixed yet?

◆After a form of the auxiliary be in the passive voice

The radio was fixed on Monday.

◆After the verbs have and get with a causative meaning

We had the radio fixed last week.