Choose the word or phrase among A, B, C or D that best fits the blank space in the following passage.

City planners have claimed trees (1)…… an important role in an urban environment. Children (2)…….. close to nature have better health, while walking in parks helps reduce blood pressure, stress and obesity. The problem is to select the right trees and (3)…… them.Ha Noi is considered one of the greenest cities in Viet Nam thanks to its beautiful and precious trees. Ancient trees in Ha Noi are frequently (4)……. in poems. Each street can be (5)……… by a tree. To local residents, the hundred-year old trees that line the streets are more than just beautiful, they are part of the city's identity. Due to the treasured place the trees have in the (6)………… of the local residents, Hanoians seem to have a lot of concern when construction workers chop them (7)………. Workers get away with digging around the trees without much care, and even (8)………. the trees without enough earth to grow - making them vulnerable to storms.To (9)……… with the problem, Ha Noi's authorities have started a project of replanting trees: each of the capital's streets will be planted with two or three sorts of trees. Moreover, more people should be made (10)…… of the importance of protecting trees in communities. 

City planners have claimed trees (1)…… an important role in an urban environment.