The birdcage effect is a psychological concept. It means that people will accidentally obtain an item that is not needed, and continue to add more related things that they don't need. According to the above definition, Which of the following are consistent with the birdcage effect:. ['Wenwen bought online and bought several items more than expected in order to participate in the "full reduction" activity.', "Aunt Liu went to the supermarket to buy groceries, and found that the cleaning supplies happened to be on sale, and couldn't help but buy a bunch.", 'Lili bought a skirt and gave it a sweater chain. She felt that there was no sweater to match, and she bought another sweater, but she never wore it.', "Xiaoling's boyfriend gave her a bouquet of flowers. She was very happy and went to buy a beautiful vase."]