Um I think it might be "that"
Child birth is the answe i think....................................
You should place commas around a phrase the at adds additional information to the sentence, but which is not necessary.
1)<span>Tanna president of the National Honor Society truly enjoys volunteer work.
this part is not necessary, so commas are required before and after it
2) The old house, that my father grew up in, is being completely renovated.
here the commas are unnecessary! that's because we need the information in boldface to identify the house
4) </span><span><span>My sister, who is a waitress at Billy’s Big Burger Shack, is sixteen years old.</span>
this is a correctly punctuated sentence - the information about being a waitress is additional.
5) The bird that built a nest in the oak tree, appears to have an injured wing.
here either the commas should be removed, or another comma added after "bird"
</span>
<span>He used propaganda to make the people afraid of other countries and so they would believe in him, he said all these good things that were a distortion of the truth.</span>
