Denise accidentally deleted a sentence from her document. how can she replace it without retyping it?

She can click on the undo button located depending on the program she is using. (ms word: on the top left corner) 
or she can hold the ctrl button on her keyboard while she is pressing the z letter.

The type of program is the hierarchical grid

Don’t go to websites that give you viruses or bugs and don’t click random adds that are weird