In what type of star would helium be converted to carbon as the final stage of fusion?

The correct answer is red giants.  

Red giants refer to the stars, which have lost the supply of hydrogen in the cores and have started thermonuclear fusion of hydrogen in a shell enveloping the core. They have dimensions ten to hundreds of times bigger than that of the Sun. However, their outer covering is less in temperature, providing them a reddish-orange hue.  

The Sun and any kind of red dwarfs above about 0.25 solar masses, will arise into what is known as a red giant, a later phase of stellar evolution. At this phase, the star begins to combine with various elements, and finally throws off its layers as a planetary nebula, leaving behind a white dwarf of oxygen and carbon.  

the offspring would all be white. if the parents are both white flowers then they have the genotype rr, which when crossed results in an all white punnet square.