Which food was received in the temperature danger zone
milk 38f
cottage cheese at 40f
shell eggs at 43f
potato salad at 46f

The food that was received in the temperature danger zone is: Potato salad at 46F

Temperature danger zone for food exist between 40 F to 140 F.
From the option above, cottage cheese is still safe because it is made with fermentation technique. Eggs are still safe because it has shells that protect it from rottening. That leave the answer with potato salad.