Когда использовать some, а когда a/an

Some множественное число если первый пишется согласная это a. гласная первая тогда an

1) in summer they travel very much in the caucasus. или they travel very much in the caucasus in summer. 2) she teaches us english with pleasure. 3) first of all, i must tell you many things about myself. 4) he is the last person i want to see now. 5) every morning i have to wait ages for a bus at the bus stop. 6) there are lively discussions at his seminars.