题干
his work these days，he hash’t _____ when to pay a visit to his parents·
A：Bent On：decided o
B：Worried about；turned o
C：Faced with；taken o
D：Devoting to；focused o
答案(点此获取答案解析）
A
点光照强度时，适当使用二氧化碳发生器可以提高作物产量