Sentence:  Says Wallace F. Jannsen , director of the FDA 's Division of Public Information : `` Quacks are <WSD>apt</WSD> to direct their appeal directly to older people , or to sufferers from chronic ailments such as arthritis , rheumatism , diabetes , and cancer . 
Meaning of the word marked with <WSD> tags:  at risk of or subject to experiencing something usually unpleasant