Antibodies are produced when the body is exposed to antigens macrophages receptor proteins

Option A

Explanation:

Antibodies are protective proteins that are released by immune system when any foreign agent enters into our body. These harmful foreign agents are known as antigens, in response to which antibodies are produced.  

B Lymphocytes are specialized white blood cells that produce antibodies when it comes in contact with the surface of the antigen which is different from the surface of other bio molecules with in our body. After interacting with antigen, B lymphocytes divides and form a clone of identical cells. This clone then secretes millions of antibodies into the bloodstream

Hence, option A is correct

you are certainly talking about this picture:

a: is the label of the white square, it is showing the  replication fork, formed by helicase (d) ==> so it is the site of dna separation and replication 

b: is a new dna brand that is following directly the replication fork, so it is continuous ==> built continuously from 5' to 3

c: dna polymerase cannot replicate dna on its own, it needs the of their proteins, and one of them plays the role of a clamp which fixes  the dna with the dna template and increases  the processivity of the enzyme. ==>   stops polymerase from falling off the  template.

d: is the enzyme responsible for forming the replication fork (helicase) ==> unwinds and separates dna into two strands

e: is the delayed strand, it is built  in the opposite sense of the helicase, so dna will be built in fragments ==> built  fragments from 5' to 3 joins

and finally f: is the enzyme that builds  the new dna strand (dna polymerase) ==>   adds nucleotides to make a new dna helix.

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answer:   option a) glucagon was secreted by his pancreas before he ate the cookies because blood glucose was low. insulin was secreted after he ate the cookies because his blood glucose was high.

explanation: