Doctors agree that factors such as cigarette smoking, eating rich foods, and alcohol consumption not only damage by themselves but also aggravate genetic predispositions towards certain diseases.1). did damage by themselves but also aggravate2). are damaging by themselves but also aggravating3). not only do damage by themselves, they are also aggravating to4). No improvement

Doctors agree that factors such as cigarette smoking, eating rich food

1.	Doctors agree that factors such as cigarette smoking, eating rich foods, and alcohol consumption not only damage by themselves but also aggravate genetic predispositions towards certain diseases.1). did damage by themselves but also aggravate2). are damaging by themselves but also aggravating3). not only do damage by themselves, they are also aggravating to4). No improvement
Answer» Here, ‘Not only x...but ALSO y’ is CORRECTLY USED. In 1, ‘aggravating’ is incorrect as it means ‘annoying’ when used in participle form. 3 is wrong because ‘not only’ without ‘but also’ is wrong. In 1, simple PRESENT tense should have been used. Thus, the CORRECT answer is 4.