【问】 She is accustomed to reading on bed till mid-night.(攻读硕士学位研究生入学考试英语试题，83.B)
 标准答案要求将on bed(C)改为in bed.据我所知，表示“睡觉”的意思时才用in bed，上道题是说“在床上读书”，并不是说“睡觉”，那为什么也要求用in bed呢?
 【答】 不错，in bed常常表示“睡觉”的意思。例如：
 1. It’s ten o’clock in the morning but he’s still____.
 A. at the bed B. at bed
 C. in bed D. in the bed(Nelson，300C)
 2. I sometimes stay in bed until lunch time. (New Concept English，Book 2)
 有时我一直睡到吃午饭。
 3. That night we were in bed early. (Snow)
 那天晚上我们睡得很早。
 4. He lay in bed beyond his usual hour.
 他比往常睡得时间长。
 但是，in bed也可以指脱掉外衣或盖被子躺在床上读书或思考问题。例如：
 I prefer to remain in bed and dream on undisturbed.
 我喜欢躺在床上独自静静地遐想。
 on the (a) bed(注意：必须有冠词)则是在具体的床上，没有“睡觉”这一抽象含义。与之搭配的动词有sit，lie，lie down等：
 1. Joe sat on the bed while Martin unpacked. (London)
 乔坐在床上，而马丁在打开包裹。
 2. He took off his shoes and stretched himself out on the bed.
 他脱了鞋，在床上伸直了身子。
 3. Lie down on the bed. (CGEL)
 在床上躺一躺。
 4. Would you like to lie down on the bed for a few minutes? You look rather tired.(LDPV)
 请你上床躺几分钟吧!你显得有点儿疲倦。
 5. Lie on a bed of thorns
 如坐针毡
 in behalf/on behalf 见behalfin black/in the black
 【问】 请分析in black与in the black的差别。
 【答】 in black意为“穿黑衣服”，而in the black意为“有盈余”，请对比下列例句：
 1. He was dressed in black. (ALD)
 他身穿黑色衣服。
 2. The new production method put the factory in the black.
 新生产方法使工厂有了盈余。