先期脱氧的主要作用是（）。
A、脱去熔滴中的氧
B、脱去熔池中的氧
C、脱去药皮中放出的氧
参考答案：C
比0.2大比0.4小的数只有0.3．______．（判断对错）
用所给单词的适当形式填空
小题1:I had a difficult time _________ (study) English
小题2:My sister is _________ (thin) than me.
小题3:John always listens to the old man in _________ (silent).
小题4:Let’s welcome these _________ (hero) to our school.
小题5:My brother plays the guitar very ________ (good).
