IELTS Grammar: do you make this 'pronoun' mistake?

Look at the sentences below. Can you see the mistake in each one?

1. Children who play chess, they become more creative as adults.
2. A lot of political leaders, they are corrupt.
3. My brother, he is studying at university in Canada.
4. My writing exam, it was very difficult.

I've underlined the problem: each sentence contains an unnecessary pronoun. Many students make this mistake, especially when speaking. If you can avoid it, your English will sound much more natural.

Here are the correct versions:

1. Children who play chess become more creative as adults.
2. A lot of political leaders are corrupt.
3. My brother is studying at university in Canada.
4. My writing exam was very difficult.