Choose the best topic sentence from the four options below.

Choose the best topic sentence from the four options below.
A、Apart from the local economy, we should also consider the environment when talking of tourism.
B、Some tourists leave waste and make noise, which seriously disturbs animals and local inhabitants.
C、Touring by car will produce many poisonous and harmful gases, such as carbon dioxide and nitrogen dioxide.
D、Tourism is one of the biggest industries of our time and is generating around 9.5% of the world's total GDP.
【正确答案】：A