A、It hasn’t been fully tested. B、It is not economical enough. C、The gas it produces may cause explosions. D、The gas it produces

W: Hi, Jim. What are you doing?
M: Oh, hi, Linda. I’m working on a report on energy resources for my environmental science class. But I’m having trouble finding enough information.
W: You know, we were talking about sources of fuel in my class today.      
M: Yeah?                 
W: Prof. Collins. He is an authority on energy sources. He was telling us about a new way of getting fuel oil from coal.     
M: I didn’t know that was possible.
W: He said something about coal being set on fire and blasted with a mixture of steam and oxygen. This process produces a gas made up of hydrogen and carbon, and the...hum, the basic elements of oil.
M: And then do something to change that gas to oil?
W: Right. First, since coal contains fewer hydrogen atoms than oil, they have to add some extra hydrogen to the gas. Then impurities are washed out with methanol, I think, before this gas is sent to reactors where it’s changed into oil.            
M: Since coal is so plentiful, I guess it won’t be long till this new type of oil is available all over the place, huh?
W: I doubt it. Prof. Collins said something about the process not being economical enough to use in this country. At any rate, you really ought to talk to him. He’ll be able to help you more than I can and he’s got office hours all afternoon today.           
M: Thanks. He’s over in Anderson Hall, right?         
W: Right.
Questions 5 to 8 are based on the conversation you have just heard.
5.What trouble does the man have?
6.What are the speakers mainly discussing?         
7.What will generate initially in the process of getting fuel oil from coal?
8.What is the disadvantage of the new way of getting fuel oil from coal according to Prof. Collins?