Wstaw w odpowiedniej formie (czasie) czasowniki z nawiasów oraz wyrażenia "for" i "since"
Tropical rainforests have been an important lofe force on Earth ________ the beginning of time. They ____________ (help) to keep the air we breathe fresh and clean ______ millions of years. ______ the last fifty years, however, we ________ (cause) a lot of damage by cutting them down for industrial purposes.
Deforestation __________ (be) a problem _______ the middle of the nineteenth century, when the industrial revolution _________ (start). The problem ________ (grow) more and more quickly ______ then, and _______ the last two decades, we _______ ( reduce) our rainforests at the rate about 100 000 squaere kilometers every year.