subject
1. The components of the subject: nouns, pronouns, non-predicate verbs, clauses (guide words + sentences)
2. Can the subject be less
If there is no subject:
1) Add it as the subject: it must be related to weather, temperature, and time
2) There be sentence pattern, used when you hear "Yes"
3) Passive: When you hear a sentence without a subject or a personal pronoun as the subject, you can consider writing it as passive
4) Personal pronouns as the subject: it is not a last resort, it is best not to use it,
Three situations are not passive:
1) If there is a preposition after the verb, the verb is not passive
2) Copulative verbs are not passive
3) Have no passivity when expressing the meaning of "have"