On page 38 what does the picture of the fort tell you about portuguese explorers explain in complete sentences.

1)when the explorers travel they have something to look at 
2)they can do some historical research on them 
3)that they had some attacks and the fort was used as a defend its position
These are some that you could use i strongly suggest you use the third one 
Hope this helps:)

The answer is monsoons.

Its a whole new world