【单选题】Green-space facilities are contributing to an important extent to the quality of the urban environment. Fortunately it is no longer necessary that every lecture or every book about this subject has to...
【简答题】There are 1200 elephants in a herd. Some have pink and green stripes, some are all pink and some are all blue. One third are pure pink. Is it true that 400 elephants are definitely blue?