The word "tenuous" (4th paragraph) most probably mean ______.

A．John Donne contributed to medical development through the medical
B．There has been no fantastic spurt in medical development until the present century
C．Medical development has led to the rise in infant mortality
D．Medical development will bring us a bright future

A．the fact that they are deprived of the right to health
B．their heavy investment in medicare
C．their too high expectation of what medical service can do for them
D．their being too emotional