第21题: [单项选择]从点燃紫外线灯到水银蒸气压力达一定程度,灯管工作进入稳定状态()。 A. 约需6~9min,灯管从稳定到冷却约需8~10min B. 约需8~11min,灯管从稳定到冷却约需8~10min C. 约需10~13min,灯管从稳定到冷却约需8~10min D. 约需12~15min,灯管从稳定到冷却约需8~10min E. 约需14~17min,灯管从稳定到冷却约需8~10min 参考答案:D
第33题: [单项选择]She didn't know ______. ( ) A. where she gets the book B. where would she get the book C. where getting the book D. where to get the book 参考答案:D