英文Grammar~~

1. There are two clauses here. The first clause is I walked down the stair, and the second clause is (I) saw a ghost, in which the pronoun "I" is omitted. These two clause is joined by the coordinator "and"

There are two main verbs in the sentence above. They are "walked" nad "saw" as these two verbs are marked by tense - simple present tense here.

Please compare the following sentence:

1a) Hoping to see a ghost, I walked down the stair.

There are, again, two clauses. One is "Hoping to see a ghost" and the other one is "I walked down the stair". However, this time, there is only one main verb" walked" and it is marked by simple past tense.
What about "Hoping" and "to see". They are called non-finite verbs as they are not marked by tense or number.

A sentence usually has one main verb:
1. I always play compute games. (main verb: play)
2. She usually goes to school on foot. (main verb: goes)

The are more than one verb in the following sentence
1. She likes singing and I like drawing. (main verbs: likes and like)
2. John went to the supermarket last week, but she did not believe (main verbs: went and believe)

2. You are talking about reported speech here.
It seems that it is more correct to say "Yesterday, he said that the sun rose every day" because you are talking abotut what happened yesterday. (i.e. he said something)

But in some situations, we can say,
The reporter said that the weather is fine tomorrow.
We can see that we don't change "is" to "was" and "tomorrow" to "the following day". The reason is to convey the sense of immediacy and "the weather is fine tomorrow" is still valid. Or you're immediately reporting what the reporter said to a third party.

1)I walked down the stair是clause
(clause= 完整sentence) 後面的sentence 只是補充
clause入面的verb 永遠都唔係main verb
而且一個句子唔可以有多過1個main verb
main verb是saw

2)用tense 係depend on 件事發生個time

Yesterday, he said that the Sun rase every day.岩
said,heard+ that後面是past tense