4. How many trees does it take to Provide a day's supply of oxygen For 4 people? a) 1
b) 5
c) 30
d) 50

1 tree provide oxygen to 4 people in a day

the development of trade during the middle age increased to the change given in the agriculture, which gave money, industry and markets a bigger importance in economy. the agriculture production was more than the consumption, which meant the creation of wider markets out of the areas. besides, with the end of multiple wars, the population increased and new trade routes were created.