Read this excerpt from The Golem.

Rabbi Low looks expectantly at the Golem.

Thunder sounds in the distance. Rabbi Low checks his papers. He repeats the words, louder this time.

There's more thunder, closer this time. It begins to rain. Still nothing from the Golem. Rabbi Low shouts the words, partly in desperation, partly to be heard over the howling wind.

What is the effect of the stage directions?

They build suspense.
They build the plot.
They build exposition.
They build character development.