What effect does the final dash have in this brief poem by Emily Dickinson?

What I can do—I will—
Though it be little as a Daffodil—
That I cannot—must be—
Unknown to possibility—

It reminds readers how much a daffodil matters in the world.

It is used to brag about her contribution to literature.

It suggests the speaker is unsure what she can and will do.

It invites others to join her in writing poetry.​