Вариант 63

In Moscow, there are approximately 35,000 dogs living on the streets. Some of these (29) animals were born there. Others are just (30) pets that have been abandoned by their owners. For many dogs the city may be a (31) place to live in. However, scientists were surprised to find out how (32) some animals can adapt to urban life. Some dogs have even learnt to use the city’s metro system! We still don't know how the dogs find out when to get off the train. One (33) is that they use their excellent sense of smell to recognise the scents of their favourite destinations. Another idea is that they are able to remember the design of (34) stations and find the station they need.