Choose your reply from the options at the end. Does "In this case, xenodiagnosis involves the use of the vector of the Chagas agent T. cruzi, an uninfected triatomine bug, which takes a blood meal from a person suspected of having been infected." contain the correct answer to "What is it difficult to demonstrate the presence of in Chagas disease?"
Available choices:
(a). yes;
(b). no;
(b).