Pollen grains taken from one plant were put onto the stigma of a flower on the same plant. The lengths of the pollen tubes were measured over four hours. (In this species of plant, the mean length of the style is $2\,\text{mm}$.) This was then repeated with pollen from a different plant. The results are shown. Which statements are correct?
- A1, 2 and 3
- B1 and 2 only
- C1 and 3 only
- D2 and 3 only