a)
The girl talking to Tom - Девушка разговаривающая с Томом.
The plane flying in the sky - Летящий в небе самолет.
The bird singing in the tree - Поющая на дереве птица..
The rising sun - Восходящее солнце.
The children swimming in the sea - Ребенок плавающий в море.
Factories producing food - Фабрики производящие продукты питания.
People living in towns - Люди живущие в городах.
b)
1) The girl talking to Tom is his sister.
2) There were many clouds and we could not see the rising sun.
3) The bird singing in the tree is not a pigeon, dear.
4) Let's get up early tomorrow and go and watch the plane flying in the sky.
5) The children swimming in the sea were laughing loudly.