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Some textbooks say there should be incoherence of tenses between the main clause and the objective clause under the following circumstances which are divided in 4 categories. Are they right with what they say? And if so, do I have to follow these examples next time I want to these types of sentences?

1. Long ago people didn't know that the earth moves round the sun. She told her son that practice makes perfect.

2. The teacher told us that the attraction of the earth for all bodies is called gravity.

3.He said he does morning exercises every day.

4. John said his father is attending a meeting in . She told me the other day that she is only seventeen.

Many thanks.
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Incoherence should never be tolerated, but as far as your sentence are concerned, these are OK:

1. Long ago people didn't know that the earth moves/moved round the sun. She told her son that practice made/makes perfect. ('Makes' is probably more usual because it is a proverb.)

2. The teacher told us that the attraction of the earth for all bodies was/is called gravity.

3.He said he did/does morning exercises every day.
4. John said his father was/is attending a meeting in Shanghai. She told me the other day that she was/is only seventeen.

I have underlined the ones which I think a native would usually use. Statements that remain true today are usually regressed with the main verb unless they are very obviously 'universal truths', like 'She explained to us that water boils at 212 degrees Fahrenheit'.
Comments  
Thank you, sir. Your detailed and expertise explanation makes me feel I owe you. Thank you again.