A group of students was examining the moss Pterogonium gracile. Diagram of a pterogonium gracile moss. A is a tall stalk. B is one of many branches, on which are diamond-shaped leaves.

The moss was found to have two structures:

A. A tall stalk structure that was present only in spring when the moss produced spores.
B. A brownish-green or brown branching structure that was present year-round.

The students produced several hypotheses about how the moss reproduced.

I. The branching structure is diploid and undergoes mitosis to produce the stalk.
II. The branching structure is haploid and undergoes meiosis to produce the stalk.
III. The stalk is haploid and undergoes mitosis to produce the branching structure.
IV. The stalk is diploid and undergoes meiosis to produce the branching structure.

When the students examined the moss, they found the stalk had 11 pairs of chromosomes and the branching structure had 11 chromosomes. Which hypothesis does this information support?

I
II
III
IV