Once environmental damage_____, it takes hundreds of years for the system to recover.A．has

Once environmental damage __________,选择

A huge amount of environmental damage has been brought_____by the destruction of the rainf

Taking photographs is strictly______here, as it may damage the precious cave paintings. （2

Once damage______, it takes many years for the natural environment to recover.A．has doneB．

It was once believed_______ and thus we can tell

It was once believed_________ and thus we can tel