Answers:
1. A
2. B
3. B
4. A
Analysis:
“不止 (Bùzhǐ)” is often used to indicate that it is not limited to a certain number or scope. It is equivalent to “more than”.
“不只 (Bùzhǐ)” is a conjunction, which is used in complex sentences of progressive relations. It is equivalent to “not only”.
Zhè tǒng shuǐ bùzhǐ shí gōngjīn.
1. 这桶水不止十公斤。
This bucket of water is more than ten kilograms.
Bùzhǐ wǒ yǒu nà běn shū, tā yě yǒu.
2. 不只我有那本书，他也有。
Not only do I have that book, but he also has it.
Pǎobù bùzhǐ kěyǐ jiǎnféi, hái kěyǐ duànliàn shēntǐ.
3. 跑步不只可以减肥，还可以锻炼身体。
Running can not only lose weight but also exercise your body.
Nǐ kànqǐlái bùzhǐ èrshí suì.
4. 你看起来不止二十岁。
You look more than twenty years old.