In a Capture Assay for IgM That Reacts with Rubella

In a capture assay for IgM that reacts with rubella, an antibody to human IgM binds the patient IgM, rubella antigen from the kit is added, and then an enzyme labeled antibody to rubella is added. What would happen to this assay if the patient had rheumatoid factor but no IgM antibodies to rubella?

A) The patient would appear positive for IgM rubella antibodies unless bovine serum albumin was added as a nonspecific blocker.
B) The patient would appear positive for IgM rubella antibodies unless nonfat dried milk was added as a nonspecific blocker.
C) The patient would appear positive for IgM rubella antibodies unless human IgG that did not react with rubella was added as a specific blocker.
D) The patient would appear negative for IgM rubella antibodies unless human IgG that did not react with rubella was added as a specific blocker.