What is the dryness fraction $($quality$,$x$)$ for saturated water when water just starts boiling?

Question $12$Select one:

A$.$

x$=0\mathrm{.}5$x$=0\mathrm{.}5$

B$.$

x$=0\mathrm{.}9$x$=0\mathrm{.}9$

C$.$

x$=1$x$=1$

D$.$

x$=0$