Когда пишется артикаль an, а когда a ?

Насколько я помню "an" пишется, если следующее слово начинается с гласной буквы, а "a" в остальных случаях, но по моему есть ещё какие то исключения

1. janny is from london. she speaks english. – yes, he did. jerry understood her. 2.  fiona is from italy. she speaks italian. – no, he didn't. jerry didn't understand her. 3.  boris is from russia. he speaks russian. – no, he didn't. jerry didn't understand him. 4.  alise is from france. she speaks french. – yes, he did. jerry understood her. 5.  wendy is from glasgow. she speaks english. – yes, he did. jerry understood her. 6.  fred is from leeds. he speaks english. – yes, he did. jerry understood him 7. ken is from paris. he speaks french. – yes, he did. jerry understood him

1. she said they were impressed. -  она сказала, что они были впечатлены.

2. we said nobody could help us. -    мы сказали, что никто не мог нам .

3. you said you had bought a good car that day. -  вы сказали, что вы купили хорошую машину сегодня.

4. we said we were working on a new model at that time. -  мы сказали, что мы работали над новой моделью в то время.

5. they said they had been offered a job by them. -  они сказали, что им предложили работу.

6. i asked what they had thought about that. -  я спросила, что они думали об этом.

7. she said she would come to the meeting. - она сказала, что придет на встречу.