引起急性肠梗阻的肠扭转角度至少是（）。

A.90°

B.180°

C.270°

D.360°

E.540°

Which of the following statements is closest in meaning to the passage you have just heard().

A. There is plenty of grain in the world and people need not to worry about it.

B. The world’s population is estimated to explode from over 6 billion now to 19 billion by 2050.

C. The population increase is mainly in undeveloped countries.

D. World demand for foods is predicted to rise 50% by 2030.