Противоположное прилогательное к слову dirty знаю что первая буква: с и там 5 букв

Clean- чистый dirty- грязный  пара антонимов

Clean чистый, dirty   грязный

Хз мб вот это  for the first time the idea of building the underground railway in moscow was discussed before the revolution. but the construction of the first section (from sokolniki to central park) was initiated only in 1932, and lasted 3 years. it was called the record period of time by the world press. the russian engineers carefully studied the existing underground systems abroad before working out their own project, which represents a significant improvement on the london system. the engineering difficulties were great mainly because much of the soil was composed of running sand*. fortunately most of the running sand lay close to the surface and it was found possible to use out-and-cover method** of construction under many of the streets. but in the center of the city where the line is 100 ft or more deep, the construction of tunnels was necessary. the moscow underground consists of a circle line, which runs round the city center, several radial lines crossing the city and connecting with each other and the lines running to the countryside. some constructional work is still going on. now the length of the underground lines reaches about 300 km. at present the moscow metro handles more than 5 million passengers each day. during peak hours trains run at a speed of 90 km per hour with the intervals of about 80 seconds. one train takes up to 1,500 passengers. for greater safety of travel all trains are inspected every 6-9 hours of running. being in operation for about 13 hours daily each metro train covers the distance equal to that from moscow to st. petersburg. the trains servicing the underground are supplied with low voltage direct current. the current is obtained from the third rail by special devices that are mounted beneath the motor coaches. rolling stock is completely replaced approximately once every four years. the moscow metro can compete with the underground railways in any of the european capitals in level of automation. at present experiments are being conducted with an “automatic driver”, i.e. with computer-controlled trains. the computer devices will help to relieve the nervous strain on the drivers and make it possible to increase the cruising speed*** of trains even more. these automatic devices have already been tested over the circle route by way of experiment. 

There are many problems in our world, different countries and organizations. but there is a problem that's disturbing all the world. our planet is full of industrial factories and plants. millions of cars are emitting some harmful substances into the air. such substances make people and animal suffer from polluted air. our industry is a cause of global warming and we can't stop it right now due to lack of technology development.  however, all is not so bad. we have thousands of organizations and even corporations that are trying to popularize alternative energy sources. and their work is noticeable. electric automobiles are becoming more and more popular. plants and factories are using modern technologies to reduce emissions. somebody could say "hey, you're too optimistic and we all are going to the abyss." but i'm not an optimist, i just see all the improvements last years that are believed to change the situation all over the world.  you and i have only to help in this by promoting new harmless technologies. maybe they aren't too profitable right now, but someday they will replace old and harmful one.  i believe that our future world will not be a big trash. it will be a pretty place with beautiful nature and complementary synthesis of nature and technology.