At room temperature which of the following species is/are present in polymeric form.

Options

A. `AlH_(3)`
B. `BF_(3)`
C. `BN`
D. `BeCl_(2)`

Answer

To determine which species are present in polymeric form at room temperature, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Identify the Species**: The question mentions several species: AlH3, BF3, BN, and BeCl2. We need to evaluate each of these to see if they exist in a polymeric form at room temperature.

2. **Evaluate AlH3**:
- Aluminum hydride (AlH3) is known to exist in a polymeric form at room temperature. It has a structure where AlH3 units are linked together, forming a polymeric network. Thus, AlH3 is present in polymeric form.

3. **Evaluate BF3**:
- Boron trifluoride (BF3) is typically a molecular compound and does not form polymers at room temperature. It exists as discrete BF3 molecules and does not exhibit polymeric characteristics.

4. **Evaluate BN**:
- Boron nitride (BN) can exist in various forms, including hexagonal and cubic structures. However, at room temperature, it is generally not considered to be in a polymeric form but rather as a solid with a defined structure.

5. **Evaluate BeCl2**:
- Beryllium chloride (BeCl2) can form a polymeric structure in the solid state, but at room temperature, it is often found in a dimeric form rather than a true polymeric form. Therefore, it does not qualify as being in polymeric form at room temperature.

6. **Conclusion**:
- Based on the evaluations, only AlH3 is present in polymeric form at room temperature. The other species (BF3, BN, BeCl2) do not exist in polymeric form under these conditions.

### Final Answer:
The species that is present in polymeric form at room temperature is **AlH3**.