Once upon a time, cars were regarded as one of the most valuable inventions. However, a series of problems followed it are obvious, such as, the exclusion of carbon dioxide, traffic jam.
To be gratified, scientists seeking the way of solving problems are working hard. The invention of electric vehicle eases the global warming pressure to some extent. At the same time, the increasing awareness of taking buess is helpful to traffic jam.
As we all known, people always prefer to live in a sound environment, not a worse one. Keeping the environment clean is our duty.