单项选择题
Most authorities believe that urban street crime from a combination of poverty, poor education and a lack of opportunity. ________.
单项选择题 The doctor told the students that an ________ disease was one that could be passed from one person to another.
单项选择题 There was a noisy ________ at the back of the hall when the speaker began his address.
单项选择题 The scientists were ________ as they had found not one but three viruses.
