省煤器管子排列方式有哪几种？
参考答案：
省煤器蛇形管按其排列方式可分为顺列布置和错列布置两种。
比米大的长度单位是______，比厘米小的长度单位是______，比千克大的质量单位是______．
— John called' you yesterday but you didn't answer the phone.
— Oh, I ________ flowers in the garden at that time. [ ]
A. watered
B. am watering
C. was watering
D. have watered
