英语高手进来

when表示一个时间点
during表示一个时间段
区别二者主要看句意，如果明显是一段时间就用后者，如果明显是一个时刻如5点就用前者。
此题选A啦
牛津高阶英汉双解词典

while 1
/ waɪl; US hwaɪl; hwaɪl/ n [sing]
(period of) time （一段）时间: She worked in a bank for a while before studying law. 她学法律之前在银行工作过一段时间. * For a long while we had no news of him. 很长一段时间我们没有他的消息. * I'll be back in a little while, ie soon. 我一会儿就回来. * It took quite a while (ie a long time) to find a hotel. 很长时间才找到一家旅馆. * We waited for three hours, all the while hoping that someone would come and fetch us. 我们等候了三个小时, 一直希望能有人来接我们.
(idm 习语) once in a while => once. worth sb's while => worth.
> while v (phr v) while sth away pass (a period of time) in a leisurely way 逍遥自在地度过（一段时间）: We whiled away the time at the airport reading magazines. 我们在机场阅读杂志消磨时间. * It's easy to while a few hours away in a museum. 在博物馆里很容易打发掉几个小时.

while 2
/ waɪl; US hwaɪl; hwaɪl/ (also whilst / waɪlst; US hwaɪlst; hwaɪlst/) conj
(a) during the time that; when 在...期间; 当...的时候: He fell asleep while (he was) doing his homework. 他做着做着功课就睡着了. * While I was in Madrid there was a carnival. 我在马德里的时候正赶上狂欢节. * While (locked up) in prison, she wrote her first novel. 她在狱中写出了第一部小说. (b) at the same time as 与...同时: While Mary was writing a letter, the children were playing outside. 玛丽写信时孩子都在外面玩儿. * He listens to the radio while driving to work. 他去上班一边开着车一边听音乐. * I lived in a hostel while I was a student. 我求学期间住在青年招待所里.
(used to show a contrast 用以表示对比或相反的情况): I drink black coffee while he prefers it with cream. 我爱喝清咖啡而他喜欢加奶油的. * English is understood all over the world while Turkish is spoken by only a few people outside Turkey itself. 英语世界通行, 但土耳其语离开本国就很少有人说了.
(fml 文) although 虽然: While I admit that there are problems, I don't agree that they cannot be solved. 尽管我承认有问题存在, 但我不同意说这些问题不能解决.牛津高阶英语词典

when是连词，接句子~~during是介词，只能接词，不能接句子~~

选A--while,

when除了可以加时间段，还可以加时间点，

而while只可以加时间段，
这里强调时间段（布朗先生呆在天津的那几天，他参观了许多名胜古迹),所以最好用while~~^_^

during不能引导句子，

among也是介词，不能加句子，是在...之中的意思，不是在什么期间~~正确用法举例：
among these students,she is the best----在这些学生中，她是最棒的~！

首先意思不同，when——当...时，during——在...时期中。
其次during是介词，后面只能跟介词短语，不能跟句子，而when却能跟句子。
由于你的题目中he was staying in Tianjin 是一个句子，因此只能选when

选A，过去进行时，是一种状态，用while
when + 一个特定的时间点。如：Please call me when you leave.这里的
when you leave就是一个时间点
而during + 一个时间段。如:During these years\During the five years\
During the holiday……
希望能帮到你

during后面接名词：I went to visit the Great Wall during the summer vacation.我暑假里去游览了长城。
when,while都意为“当…”，都引导时间状语从句。
when强调时间点，通常译为“当…”，例如：
When she came in, I was cooking. 她进来时，我正在做饭。

我感觉是选C的。

When的意思是：当...的时候，表示一个时间点。
而during表示一段时间。
比如：when did you meet Micheal？
意思是：你什么时候遇到michael？注意是什么时候。
I am studying in school during 8.1 to8.5意思是我1至5号在这段时间学习。是一段时间。

这个题说布朗先生在天津玩，肯定是一段时间。所以选c