1.underline the correct word. 1)zoos play an important role/ cycle in animal conservation. 2)cars burn/ emit petrol. 3)animals should live in their natural ecology/ habitat. 4)acid rain causes/ poisons trees and plants. 2.complete with the present perfect continuous form of the verb in brackets. 1)he… (work) here for over ten years. 2)jill… (swim) in this lake since she was a child. 3)how long … (you/ take care) of this injured bird? 4)they … (study) very hard for their exams. 5)my parents … (donate) to wwf for a long time. 6)the government … (try) to reduce pollution for years. 3.underline the correct form. 1)they have talked/ have been talking about it all morning. 2)he’s not here because he has been going/ has gone to work. he’ll be back at 4 o’clock. 3)the children cleaned/ have been cleaning the playground yesterday. 4)she has studied/ has been studying all day. 5)i worked/ have been working without a break since 8 o’clock. 6)i have been walking/ walked to the park last week.