Look at the following question from Cambridge IELTS 9, page 85:
The exact proportion of land devoted to private gardens was confirmed by
A) consulting some official documents
B) taking large-scale photos
C) discussions with town surveyors
Heres what the speaker says:
The first thing we did was to establish what proportion of the urban land is taken up by private gardens. We estimated that it was about one fifth, and this was endorsed by looking at large-scale usage maps in the town land survey office.
Here are the keywords that help you to get the correct answer (A):
proportion of land devoted to = proportion of land taken up by
confirmed by = endorsed by
consulting = looking at
official documents = maps in the town land survey office
Did you notice that answers B and C contain some keywords to trick you?