After mary murdered her husband how does she create her alibi
(lamb to the slaughter)

After she kills her husband, she put the meat into the oven then she goes upstairs in her bedroom and practices in front of the mirror what she will say and how she will act when the police show up and ask her questions and puts on little make up to get herself ready. She leaves the house and goes to the grocery store and she buys Idaho potatoes, peas and a slice of cheesecake for her husband.

And now, she told herself as she hurried back, all she was doing now, she was returning home to her husband and he was waiting for his supper; and she must cook it good, and make it as tasty as possible because the poor man was tired; and if, when she entered the house, she happened to find anything unusual, or tragic, or terrible, then naturally it would be a shock and she'd become frantic with grief and Horror. Mind you, she wasn't expecting to find anything. She was just going home with the vegetables. Mrs. Patrick Maloney going home with the vegetables on Thursday evening to cook supper for her husband.

That's the way, she told herself. Do everything right and natural. Keep things absolutely natural and there will be no need for any acting at all.

Therefore, when she entered the kitchen by the back door, she was humming a little tune to herself and smiling.

the correct answer is:

this is an example of the writer telling through description rather than showing through dialogue.

sometimes writers like to explain explicitely what's happening instead of adding dialogues of the situations., which is the case in this passage,