根据《地表水环境质量标准》(GB 3838—2002)的Ⅲ类标准，BOD5的标准限值是 ( )mg/l。
A．6
B．5
C．4
D．3
参考答案：C
After the new technique was introduced，the factory produced ________ tractors in 1988 as the year before.
A．as twice many
B．as many twice
C．twice as many
D．twice many as
左宗棠在收复新疆时，制订了“先北后南，缓进急战”的战略方针。结合所学地理、历史知识谈谈你对他这一策略是如何理解的。
