1. I heard the weather is usually windy and foggy on Dokdo.

Question

2. I heard that he is very kind.
2-2. I heard that he was very kind.
(What is the difference between them in meaning? Are both okay? Which one is commonly used?)

3. I heard that two times five is ten.
4. I heard that the earth is round.
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Are they all grammatical? The tense is different in the main clause and the subordinate clause.

Answer 1

1. OK

2 and 2-2. OK
(2-2 implies that "he" is no longer alive.)

3 and 4. OK, even with the tense differences.