Which of the Following Limits the Size of a Hornwort's

Which of the following limits the size of a hornwort's sporophyte?

A) The sporophyte's ability to distribute water to all its cells
B) The gametophyte's ability to produce enough nutrients for the sporophyte
C) Developmental genes that prevent growth of the sporophyte beyond a certain size
D) A tendency to collapse under its own weight once it grows beyond a certain size
E) All of the above