Which of the following sentences expresses “probability”? [A] You can get there in 20 minutes' walk. [B] He couldn't walk any step farther. [C] The news can't be true. [D] Could I take this home?
【单选题】The development of these gene technologies may be far in the future, but the moral and social issues raised by them should be discussed______, for once a technology has been______, it may be difficult...