Which immunoglobulin(s) help(s) initiate the classic complement pathway?

The term antibody titer is defined as:

A serological reaction is set up in which the antigen and antibody are both soluble and form an insoluble complex that is detected macroscopically. What type of assay was described?

Measurement of light scattered at an angle used to quantitate antigen–antibody complexes best describes:

Which of the following pairings of immunoglobulin and property are true?

Which molecules are found in all three pathways?

Which T cell surface protein is associated with the T-cell receptor and is involved in signal transduction?

Which immunoglobulin causes allergic reactions due to release of histamine from mast cells?

Which antibody agglutinates and fixes complement best?

Which immunoglobulin appears in the highest titer (concentration) in the secondary response?