You will hear five persons talking about different things. Decide the subject of their talk by the speaker. Write one letter(

It showed a population of 1，008，175，288，or one-quarter of the human race．There was a nineteen-point questionnaire to complete，and with the help of twenty-nine computers the information was broken into categories such as age，occupation and marital status．

A kind of oil-eating bacteria has been developed in the laboratories．They are sprayed from a plane in a sort of powder form and then，when they fall on the water，they begin to breed and multiply．Their energy，you see, comes from oil．