单项选择题
A. is threatening USA B. is threatening Great Britain C. is threatening USA and Great Britain D. is threatening outside Great Britain
A. Many animals have poor eyesight while their sense of smell, is quite good. B. Dogs are color blind. C. The human sense of smell is not good. D. Dogs can see no more than shades of gray.
A. is B. is to be C. are D. are to be