2. Having attended a conference on nature conservation, Quang became more involved in environmental activities.

3. Mai regretted having dumped / dumping rubbish in the country park near her house.

4. The manager denied having allowed / allowing harmful gases to emit into the air from the factory.

1. Having lived near a chemical plant for many years, some villagers have now developed cancer.

2. Having attended a conference on nature conservation, Quang became more involved in environmental activities.

3. Mai regretted having dumped / dumping rubbish in the country park near her house.

4. The manager denied having allowed / allowing harmful gases to emit into the air from the factory.

5. They suspected Tom of having used / using explosives to kill fish in the lake.