微台阶法台阶长度一般为（）。
A.1~2m
B.3~5m
C.5~7m
D.7~10m
参考答案：B
I won't watch TV ______ I finish my homework. [ ]
A. while
B. after
C. until
D. as
稀喂法对断奶仔猪有什么好处？
