In this task, you are given a question and answer options for that question. Using this information, you have to classify each text into different topics: medicine, nursery, psychology, chemistry, pharmacology, biology.

Question: The eggs are operculated: 
 Options:  <0> Hymenolepis nana. <1> Trichinella spiralis. <2> Enterobius vermicularis. <3> Fasciola hepatica. <4> Ascaris lumbricoides.
biology

Question: The tissue is avascular: 
 Options:  <0> Epithelial. <1> Conjunctive. <2> Osseous. <3> Muscular. <4> Nervous.
biology

Question: We want to study if Vitamin D can increase the incidence of breast cancer. In our area we have a population registry of cancer. To achieve our goal, all women diagnosed with breast cancer are selected from the register we have and each case pairs with two controls. What study design has been chosen? 
 Options:  <0> Prospective cohort study. <1> Cases and controls study. <2> Case-control study nested. <3> Retrospective cohort study. <4> Ecological study

medicine