In the following passage, some words have been deleted. Read the passage carefully and select the most appropriate option to fill in each blank.

First of all, planting trees should be given (1) ___________ attention. Above all, tree is the (2) ____________ of oxygen. Unfortunately, due to (3) __________ of buildings many trees have been cut down. This (4) __________ reduces the amount of oxygen in the environment. Growing (5) ___________ trees means (5) _________ oxygen. Hence, growing more trees would mean better life quality.

Select the most appropriate option to fill in blank number 1.