1.B
2.B
3.A
4.C
5.A
6.B
Answer Analysis：
1. Tā zuó tiān méi xué hàn yǔ.
1. 他 昨 天 没 学 汉 语。
He didn’t learn Chinese yesterday.
“没(méi) ” is generally used to negate things in the past. “昨天”(zuó tiān) means yesterday, which indicates a time in the past, so没(méi) is the correct answer. For example, the sentences“我没吃饭”(wǒ méi chī fàn): I didn’t eat，or “我没看电影”(wǒ méi kàn diàn yǐng): I didn’t watch movies, both indicate things that have not been done in the past.
2. Chén xiān shēng méi qù ɡuò měi ɡuó.
2. 陈 先 生 没 去 过 美 国。
Mr. Chen has never been to the U.S. before.
Whether Mr. Chen has been to America or not at this point is a matter of the past. Also, “没去过”(méi qù ɡuò) is a set phrase.
3. Mínɡ tiān shì xīnɡ qī tiān , bú shànɡ bān.
3. 明 天 是 星 期 天， 不 上 班。
Tomorrow is Sunday, people don’t need to go to work.
“不”(bù) is normally used to negate something that is happening frequently or in the future. “明天”(mínɡ tiān) is tomorrow, which indicates a time in the future, so the right answer is “不”(bù). If we change the sentence to “明天是星期天，别上班。”(mínɡ tiān shì xīnɡ qī tiān ，bié shànɡ bān): Tomorrow is Sunday, don’t go to work, it’s also true in meaning and grammar. But it’s common sense that people don’t go to work on Sundays, and “别”(bié) is normally used when advising, ordering or asking someone not to do something. Overall, “别”(bié) is not the right answer.
4. Yì qínɡ tài wēi xiǎn le ， qǐnɡ nǐ bié chū qù.
4. 疫 情 太 危 险 了， 请 你 别 出 去。
The pandemic is dangerous, please don’t go outside.
“别”(bié) is used in the sentence to indicate suggestion, order or demand.
5. Zhè gè pínɡ ɡuǒ yì diánr yě bù tián.
5. 这 个 苹 果 一 点儿 也 不 甜。
This apple is not sweet at all.
“一点 儿 也不”(yì dián ér yě bù) is a set phrase. And in “不甜”(bù tián), 甜(tián) is an adjective. The negative word of an adjective is “不”(bù).
6. Shǐ mì sī méi yǒu hěn duō zhōnɡ ɡuó péng yǒu.
6. 史 密 斯 没 有 很 多 中 国 朋 友。
Smith doesn’t have many Chinese friends.
The negative word of “有”(yǒu) is “没有”(méi yǒu).