4 Complete the sentences with the correct form of the words in 3. 1 Approximately 15% of the world population are of Mandarin. 2 Alice's children went to primary school in Germany, so they German without any problem. 3 Learning a language by demands a lot of effort. 4 A linguist the structure and use of language. 5 There are 41 million people (13% of the population) in the US whose is Spanish.

1. Approximately 15% of the world population are speakers of Mandarin.
2. Alice's children went to primary school in Germany, so they mastered German without any problem.
3. Learning a language by oneself demands a lot of effort.
4. A linguist researches the structure and use of language.
5. There are 41 million people (13% of the population) in the US whose mother tongue is Spanish.

Ответ: 1 - speakers, 2 - mastered, 3 - oneself, 4 - researches, 5 - mother tongue