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.

Q: Question: The simultaneous expression of IgM and IgD is observed for the first time in lymphocytes: 
 Options:  <0> Early Pro-B. <1> B mature. <2> Late Pro-B. <3> Pre-B. <4> B immature

A: biology
****
Q: Question: The number of pairs of metacentric chromosomes of the human karyotype is: 
 Options:  <0> 8 <1> 6 <2> Four. <3> 12 <4> two.

A: biology
****
Q: Question: The coupling of a terminal alkyne with vinyl halide by palladium catalysis is known as the reaction of: 
 Options:  <0> Heck <1> Suzuki <2> Sonogashira. <3> Stille <4> Nicolaou

A:
chemistry
****