Choose the word most opposite in meaning to the word 'vulnerable', as used in the passage.

Directions: Read the following passage carefully and select the most suitable answer according to the underlined word per corresponding number in the passage.

But with almost routine ways now available to test DNA samples for the presence of specific mutant genes, there is increased anxiety that an individual's genetic heritage may be vulnerable to unwanted prying. The DNA from a single human hair for example may be sufficient to alert a prospective employer or health insurer to a person's genetic predisposition to disease. Broad privacy laws must therefore be enacted to forbid genetic tests without the informed consent of the individual involved. But even with such laws, dilemmas will arise when individuals do not realise the significance of the proposed genetic screening. These tests warn of impending disease, but do not cure. And how many people would want to have certain knowledge that they will contract a disease for which there is no cure?

Banishing genetic disability must therefore be our primary concern. We would not worry about testing for a predisposing gene for Alzheimer's disease if we already had the cure. In this case, knowing that an individual is seriously predisposed might allow drug therapy to begin before brain functioning is irreversibly diminished. The recent discovery of several genes whose malfunctioning leads to Alzheimer's provides the pharmaceutical industry with important molecular targets for drug development. Only through the discovery of these kinds of genes can biomedical research stop this most pernicious cause of human senility.