a small flying animal with six legs

(of insects) to move in a large group

very tired

to eat

to make babies

to grow smaller

to enter a place gradually 

to cause sth to happen

melancholy; sadness

an illness related to the heart

to be amazed by sth

to go from one place to another

a substance (such as coal or oil) made from the remains of dead animals and plants

a mixture of smoke and fog

an accident in which oil is released into the sea

gases created from burning fossil fuels

a rise in the Earth's temperature 

the upper part of the Earth's atmosphere 

protection

liquefy

(of a boat, etc.) to overturn

to stop sth from happening

to prohibit

to make sb pay an amount of money as punishment

to put money into sth

to decrease; to lessen 

energy from the wind

energy from the sun

a series of efforts to protect the environment