Since mid-March, smog weather has frequently appeared in many cities in China, which has seriously affected people's health.

Since mid-March, smog weather has frequently appeared in many cities in China, which has seriously affected people's health. In this way, the topic is that smog weather occurs frequently, and it is reasonable that smog weather affects people's health.

Sentence: In order to express the meaning clearly, commonly used sentences include two parts: one part is the "who" or "what" said in the sentence (subject part); The other part is "what", "how" or "what to do" (predicate part) in the sentence. A complete sentence should have subject, predicate, object, attribute, form and complement.