What happens after pollen lands on the stigma of a flower? it grows a tube to travel down to the ovary. it fertilizes the plant at the stigma. it grows a tube to travel to the style. it grows a tube to travel to the petal.?

it grows a tube to travel down to the ovary

Explanation:

As a result of pollination, pollen grain lands on the sigma of the pistil or carpel.  On the stigma pollen grain begins to germinate and grows a long pollen tube.  The pollen tube grows longer and makes its way from the stigma, down the style and reaches to the ovary. Pollen tube carries two male gametes or sex cells. One male gamete fertilize the egg cell to produce zygote and the gamete fuses with polar nuclei to form primary endosperm cell.

the answer is; comparing the frequency of collisions with and without the device

this makes the anti-collision system an independent variable and the collisions a dependent variable. if there are fewer collisions with an anti-collision system that without, then it can be stated that the system is a success. essentially, collisions under an anti-collision system are compared with the frequency of collisions by cars with the human drivers.

idk what the options are but

these is a strong electrostatic attraction between the ions hence a lot of energy is needed to overcome this attraction

this is why the boiling points are so high