In a topic-comment sentence the topic may be a noun, pronoun, verb, phrase or clause. The comment usually consists of either a 是 shì phrase, a 有 yǒu phrase, an adjective or adjectival phrase:
Tā men shì yùn dòng yuán。
They are athletes.
(他们 tā men pronoun topic, 是 shì phrase as comment)
Wǒ yǒu yī gè dì dì 。
I have a younger brother.
(我 pronoun topic, 有 phrase as comment)
Zhè ér de kōng qì hěn xīn xiān 。
The air here is fresh.
(空气 kōng qì noun as topic, 很新鲜 hěn xīn xiān adjectival phrase as comment)
Chōu yān duì jiàn kāng yǒu hài 。
Smoking is bad for health.
(抽烟 chōu yān verb as topic, 有害 yǒu hài adjective as comment)
Tā chí dào shì bú duì de 。
He shouldn’t have been late. (lit. He arrive late was wrong.)
(他迟到 tā chí dào clause as topic, 是 shì phrase as comment)
 Yip, P. C., Rimmington, D., Xiaoming, Z., & Henson, R. (2009). Basic Chinese: a grammar and workbook. Taylor & Francis.