单项选择题
A.Never. B.Always. C.Usually. D.Occasionally.
A.It is becoming more accurate. B.It is more accurate than the biological sciences. C.It is more accurate than some of the measurements of structural engineers. D.It is relatively inaccurate.
A.He had forgotten to bring any food with him. B.He was afraid he would fall asleep if he should eat anything. C.He was not hungry. D.It was difficult to eat while flying a plane.