Ether which is liquid at room temperature is

Options

A. `C_(2)H_(5)OCH_(3)`
B. `CH_(3)OCH_(3)`
C. `C_(2)H_(5)OC_(2)H_(5)`
D. None of these

Explanation

To determine which ether is liquid at room temperature, we can analyze the options provided and their properties.

### Step-by-Step Solution:

1. **Understanding Ethers**: Ethers are organic compounds that contain an ether group, which is characterized by an oxygen atom connected to two alkyl or aryl groups. The general formula for ethers is R-O-R', where R and R' are hydrocarbon chains.

2. **Identifying Small Ethers**: Small ethers, particularly those with lower molecular weights, tend to be liquids at room temperature. This is due to their lower boiling points compared to larger ethers.

3. **Evaluating the Options**:
- **Option 1: Ethyl-methyl ether** - This ether has a moderate molecular weight and is typically liquid at room temperature.
- **Option 2: Dimethyl ether** - This is a small ether with a low molecular weight and is known to be a gas at room temperature, but it can be condensed into a liquid under pressure.
- **Option 3: Diethyl ether** - This ether has a higher molecular weight than dimethyl ether and is also a well-known liquid at room temperature.

4. **Conclusion**: Among the options provided, both ethyl-methyl ether and diethyl ether are liquids at room temperature. However, the question specifically asks for an ether that is liquid at room temperature, and dimethyl ether is often mentioned in the context of being a gas but can exist as a liquid under certain conditions.

### Final Answer:
The correct answer is **Diethyl ether** (Option 3) as it is a well-known ether that is liquid at room temperature.