Ответ:

1) HOw lOng have people been drinking instant cofee? — People have been drinking instant coffee since the Second World War.

2) How long haVe children been eating Cadbury`s chocolate? —  Children have been eating Cadbury`s chocolate since 1831.

3) How long have people been visiting Mcdonalds restaurants? — People have  been visiting Mcdonalds restaurants since 1947.

4) How long have British people been buying food from Chinese takeaways? — British people have been buying food from Chinese takeaways since 1974.