The correct option is (d) typhoid fever.
Explanation:
Widal test is one of the most reliable diagnostic tests for typhoid fever in developing countries since its introduction (over 100 years ago). This test demonstrates the presence of somatic (O) and flagellar (H) agglutinins to Salmonella typhi in the patients blood serum using suspensions of O and H antigens. Antigens of S. paratyphi A and S. paratyphi B are included in most commercial kits
