hey DUDE
greenhouse effect is a natural phenomenon which sustains our life by making the Earth warm and suitable for our life but it's also harmful due to pollution.
there are many greenhouse gases and one of them is carbondioxide. carbondioxide is released while burning fuels and other things and also released from cars, truck etc which causes air pollution. because of the increase of greenhouse gases (carbondioxide), more heat and radiations are being trapped and hence the temperature of Earth is rising abnormally.. and thus greenhouse effect is causing global warming. and we know how dangerous is global warming..
today we are facing so many problems and will face More in future if it's not controlled. seas and oceans are overflowing.. it's destroying polar habitats etc, many weak animals and plants are dying etc.
this way it's becoming harmful..
few ways to prevent this :-
◻ plant more and more trees since trees require carbondioxide to prepare their food by the process of photosynthesis i.e they will absorb more carbondioxide.
◻ walk or use bicycle to cover short distances.
◻ use public transport more instead of private vehicles if you are traveling alone.
◻ stop excessive use of non-biodegrable things.. and stop burning them.
◻ stop cutting trees.
Ни какие двое не могут следить друг за другом.
Пусть 001 следит за 003, тогда 003 следит за 002.
002 следит за 001, но тогда 003 следит за тем, кто следит за 001, а не за тем, кто следит за 004. Противоречие.
Пусть 001 следит за 004, тогда 004 следит за 002, 002 за 005,
005 за 003, 003 за 001 и одновременно за 006. Противоречие.
Пусть 001 следит за 005. Тогда 005 за 002, 002 за 006,
006 за 003, 003 за 007, 007 за 004, 004 за 001.
Здесь никаких противоречий нет.
ответ: 005 следит за 002.