The plural with 们
In Chinese, the suffix 们 is added to personal pronouns and some nouns referring to people to indicate plurality:
我 → 我们 we
你 → 你们 you (plural)
他 → 他们 they / them
她 → 她们 they / them (feminine)
CAUTION
们 is only used with humans. You cannot say 猫们 for "cats" (猫 = cat).
Additionally, if a number or classifier precedes the noun, do not use 们:
三个学生们 is incorrect. Simply say 三个学生.
们 can also be added to certain nouns to indicate a group:
同学们 classmates (when addressing a group)
Difference between 哪 and 什么
You may have noticed in the vocabulary that nationalities are formed by adding "person" 人 to the country name:
中国 China → 中国人 Chinese
法国 France → 法国人 French
Questions are formed by placing 哪 in place of the first syllable of the country name:
你是哪国人? Which country are you from?
哪 means "which?" when referring to a countable group (there is not an infinite number of countries).
什么 means "what?" for an uncountable quantity (there are infinitely many possible types of people).
Note
You might hear 你是什么人? to ask about nationality, but this phrasing is not elegant and could be interpreted as "What kind of person are you?" It is best avoided.
The adverb 都
都 "all" is an adverb and, like all adverbs in Chinese, it is placed before the verb (or before another adverb that comes before a verb).
Example: 我们都是法国人。 We are all French.
"Not all" is translated as 不都. Example:
她们不都说汉语。 Not all of them speak Chinese.
都不 is translated as "none" (all... not):
我的学生都不会说日语。 None of my students speak Japanese.
Examples from the dialogue:
他们都是我的同学。 They are all my classmates.
他们不都会说汉语。 Not all of them can speak Chinese.
我们都不会写汉字。 None of us can write Chinese characters.
The auxiliary verb 会
We have already seen three action verbs: 学 to study, 说 to speak, 写 to write.
The verb 会 is an auxiliary verb meaning "to know how to do something." It is placed before the verb:
他会说法语。 He knows how to speak French.
For an alternative question, the verb in question must be doubled. For example, in "Do you know how to speak Chinese?" the question concerns "knowing":
你会不会说汉语?
The particle 呢: interjection and emphasis
We learned in Unit 2 that 呢 is used to revive a question. But 呢 can also express mild surprise or emphasis.
Example from the dialogue:
她是哪国人呢? And which country is she from? (with a nuance of interest or curiosity)
Using 是不是 with 都
In the dialogue, we find the sentence:
你们是不是都学中文? Do you all study Chinese?
Here, the adverb 都 does not cause any issues with the alternative question form because it relates to the verb 学, not to 是. It is the 是 that is doubled, not the verb following 都.
Here, 是 is placed first to emphasize the sentence. This is another use of 是.