In the structure of borax, the numbers of boron atoms and B-O-B units, respectively, are

Options

A. 4 and 5
B. 4 and 3
C. 5 and 4
D. 5 and 3

Explanation

To solve the question regarding the structure of borax and determine the number of boron atoms and B-O-B units, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Chemical Formula of Borax**:
The chemical formula of borax is given as Na₂B₄O₇·10H₂O. However, for the purpose of this question, we focus on the boron and oxygen components. The boron part is B₄O₇.

2. **Count the Number of Boron Atoms**:
In the formula B₄O₇, there are 4 boron atoms.

3. **Understanding B-O-B Units**:
The B-O-B units refer to the connections between boron atoms through oxygen atoms. In the structure of borax, the four boron atoms are connected by oxygen atoms.

4. **Visualizing the Structure**:
When visualizing the structure, you can see that there are 4 boron atoms connected in a way that forms 5 B-O-B units. This is because each boron atom is connected to the next through an oxygen atom, and the arrangement allows for an additional bridging unit.

5. **Final Count**:
- Number of Boron Atoms = 4
- Number of B-O-B Units = 5

### Conclusion:
Thus, the answer to the question is that the number of boron atoms and B-O-B units respectively are 4 and 5.

### Answer:
**4 and 5**

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