Question 21:
They asked me how many children there were in the school.
 

Question 22:
The scientist said the earth goes around the sun.
 

Question 23:
The porter said that he would wake me up when the train arrived in Leeds.
 

Question 24:
He asked his girlfriend where she had been the night before.
 

Question 25:
She said that she was born in 1987, but I don’t believe. She is much younger than her age.
 

Question 21: They asked me how many children there were in the school.
Explanation: The past tense "asked" requires the verb in the past form ("were").

Question 22: The scientist said the earth goes around the sun.
Explanation: The statement is a general truth, so the present simple tense "goes" is used.

Question 23: The porter said that he would wake me up when the train arrived in Leeds.
Explanation: "Would wake" is the past form of the future tense (indirect speech), so the verb "arrived" is in the past tense.

Question 24: He asked his girlfriend where she had been the night before.
Explanation: This is a reported question, and since it refers to a past time, the past perfect tense "had been" is used.

Question 25: She said that she was born in 1987 but I don’t believe. She is much younger than her age.
Explanation: "Was born" is the correct past passive form.

Question 21: They asked me how many children there were in the school.
Explanation: In reported speech, the past tense is used, so "be" changes to "were."

Question 22: The scientist said the earth goes around the sun.
Explanation: The sentence is in the present tense because it refers to a general scientific fact.

Question 23: The porter said that he would wake me up when the train arrived in Leeds.
Explanation: "Arrived" is in the past tense because the event is reported as happening in the past.

Question 24: He asked his girlfriend where she had been the night before.
Explanation: In reported speech, when talking about an action in the past before another past action, we use the past perfect tense ("had been").

Question 25: She said that she was born in 1987 but I don’t believe. She is much younger than her age.