On the other hand，the quality of the environment is ______ by to

On the other hand，the quality of the environment is ______ by tourist development itself which is promoted because of its economic importance．
A、threatened
B、improved
C、helped
D、dropped
【正确答案】：A
【题目解析】：选项A，“threatened”的意思是“威胁”或“使……处于危险之中”。在这个语境中，由于旅游业的经济重要性而被推动的发展，可能会对环境造成负面影响，即威胁到环境的质量。这与句意相符，所以A选项正确。