Classify the following as either sexual or asexual reproduction. give the specific type if asexual.
a) a small piece of a cactus breaks off the plant, falls to the ground, and begins to grow.
b) pollen from a male poplar tree fertilizes sex cells on a female poplar tree.
c) two earthworms each produce sperm and eggs and fertilize each other.
d) aflatworm is cut in half and grows into two flatworms.