Smokers run double the risk of contracting heart disease. The word 'contracting' here means

In the context of diseases, 'contracting' means catching or acquiring a disease. For example, 'contracting an illness' = catching an illness. 'Receiving' is too neutral, 'removing' and 'avoiding' are opposites. The most accurate synonym in a medical context is 'catching'. Hence option (3) is correct.