Children have A and B type of blood. What are the blood types of parents

Options

A. A and O
B. AB and A
C. AB and O
D. A and B

Answer

To determine the blood types of the parents based on the blood types of the children (A and B), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Blood Types**:
- Blood types are determined by the presence of antigens on the surface of red blood cells. The main blood types are A, B, AB, and O.
- Type A blood has A antigens, type B has B antigens, type AB has both A and B antigens, and type O has neither.

2. **Identifying Possible Blood Types for Children**:
- The children have blood types A and B. This means one child has type A and the other has type B.

3. **Analyzing Parent Blood Type Combinations**:
- We need to consider the possible combinations of parental blood types that can produce children with blood types A and B.
- The possible blood type combinations for parents that can yield A and B children include:
- A and O
- A and A
- A and B
- B and O
- AB and O
- AB and A
- AB and B

4. **Evaluating Each Option**:
- **Option 1: A and O**: This combination can only produce children with blood type A or O, not B. So, this option is incorrect.
- **Option 2: A and A**: This combination can only produce children with blood type A. So, this option is incorrect.
- **Option 3: AB and O**: This combination can produce children with blood types A (from A in AB and O) and B (from B in AB and O). This option is correct.
- **Option 4: A and B**: This combination can produce children with blood types A, B, and AB, but not O. This option is also valid but does not directly lead to O blood type children.

5. **Conclusion**:
- The correct answer is that the parents must have blood types AB and O. This combination allows for the possibility of having children with blood types A and B.

### Final Answer:
The blood types of the parents must be AB and O.