When the
reporting verb is in the present, pesent perfect, or future tense, the
verb/s used in direct speech can be reported without any change of
tense:
The man has asked if it is raining.
When the
reporting verb is in a past tense, changes in tense forms are usually necessary:| At school | At home | |
| Teacher: What are you eating? | The student gets home and says:" Mum, the teacher asked me what I was eating and I told him I was eating a bar of chocolate." | |
| Student: I am eating a chocolate bar. |
When the student is talking to his mother, the incident he is referring to is in the past. The action expressed by "eat" is not in progress any longer. The chocolate bar is finished, so he has to use past continuous instead of present continuous.
But the change of tense is optional when the time reference of the original remark is still valid at the time we report it. Although it is optional, changes in tense forms are often preferred for the sake of concord:
Sally: I am 15 years old. If she is still 15 at the time her words are reported the speaker can say: Sally said that she was 15. Or Sally said that she is 15.