场效应管若出厂前衬底与源极相连，则漏极和源极就不能互换使用。 （ ）
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Which of the description of complement system is wrong? ( )
A. exists in body fluid
B. only takes part in adaptive immune response
C. can recruit phagocytes
D. has initiate type I hypersensitivity
Which test can be used to determine the concentration of C3/C4? ( )
A. CH50
B. ELISA
C. immunoassay
D. tuberculin test Immunoglobulins and applications
Which Ig takes part in the local mucosal immunity:
A. IgM
B. IgA
C. IgG
D. IgE
Which Ig can pass through placenta:
A. IgM
B. IgA
C. IgG
D. IgE
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