Can you help Professor Noidea? He needs help with "a" and "an"…

The pony ride is £ 4 for adults.
Let´s go fishing on island!
We sometimes spend afternoon at the zoo with our friends.
Mr Gibbson shouts a lot! He is really angry man - I don´t like him!
Let´s find new ending to the story!
I usually have apple for lunch - I love apples!
We can get into the house - look, there is open door!
Can I have ice cream, Mum? Please!
Jim falls out of tree and breaks arm.
Help! There´s insect in my ear! Help!
Let´s sing song!
Can I have orange or banana? I love fruit!
Jason is excited baby - isn´t he lovely!
I go to the shop to buy exercise book and glue stick.
Ben has got old bike. He gets new mountain bike for his birthday.
We meet Patrick and Mike at the playground in hour.
I´ve got new T-shirt. There´s elephant on my T-shirt.
The picture isn´t finished - there is ear missing! [it´s missing … es fehlt]
I often spend evening at my grandparents´ house. We play cards or watch TV.
We love animals. We have rabbits, pony and dog.
Have you got carrot or apple? I need nose and eye for my snowman!
Karen never has egg - she doesn´t like eggs.
Have you got idea for Dad´s birthday? - Yes, let´s make cake for him! - Okay!
Look! There´s owl in the tree! And there´s fox over there! Wow!
I often have orange for breakfast. I love orange juice, too.
Can I have egg, please? I love eggs!
I hate onions!
Dad sometimes has early breakfast on Sundays and goes fishing.
Sometimes he gets fish, too ;)!
Jim sometimes meets English girl at the playground - they speak for hour!
In our English book there is unit about the world´s best detective.