The antibody showing transplacental transmission is IgA/IgG.

Explanation

To answer the question regarding which antibody shows transplacental transmission, we can break down the information as follows:

### Step-by-Step Solution:

1. **Understanding Antibodies**:
- Antibodies are proteins produced by the immune system to identify and neutralize pathogens like bacteria and viruses. There are several classes of antibodies, including IgA and IgG.

2. **Passive Immunity**:
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