An organic compound containing one oxygen gives red colour with cerric ammonium nitrate solution, decolourise alkaline `KMnO_(4)`, respond indoform test and show geometrical isomerism. It should be :

Options

A. `ph-CH=CH-CH_(2)OH`
B. `pH-CH=CH-overset(OH)overset(|)(CH)-CH_(3)`
C. `ph-CH=CH-underset(O)underset(||)(C)-CH_(3)`
D.

Answer

To solve the problem, we need to analyze the given information about the organic compound and determine its structure based on the tests it responds to.

### Step-by-Step Solution:

1. **Identify the Functional Groups**:
- The compound contains **one oxygen atom**.
- It gives a **red color with ceric ammonium nitrate solution**, indicating the presence of an **alcohol** (–OH group).
- It **decolorizes alkaline KMnO4**, suggesting the presence of an **alkene** (C=C double bond).
- It **responds to the iodoform test**, indicating the presence of an **acetyl group** (–C(=O)CH3 or a methyl ketone).
- It shows **geometrical isomerism**, which is characteristic of unsymmetrical alkenes.

2. **Combine the Functional Groups**:
- From the above points, we deduce that the compound must have:
- An **alcohol group** (–OH)
- An **alkene** (C=C)
- An **acetyl group** (–C(=O)CH3 or a methyl ketone)

3. **Analyze the Options**:
- We need to check each option to see which one contains all the required functional groups and can exhibit geometrical isomerism.

- **Option A**: pH CH=CH-CH2OH
- Contains an alcohol and a double bond but lacks an acetyl group. **(Incorrect)**

- **Option B**: CH3-CH=CH-OH
- Contains an alcohol, a double bond, and has a methyl group attached to the carbon adjacent to the double bond, which can act as an acetyl group. This structure can also show geometrical isomerism. **(Correct)**

- **Option C**: CH3-CH=O
- Contains a double bond and a carbonyl group but lacks an alcohol group. **(Incorrect)**

- **Option D**: CH3-CH2-OH
- Contains an alcohol but lacks a double bond and an acetyl group. **(Incorrect)**

4. **Conclusion**:
- The only option that meets all the criteria (alcohol, alkene, acetyl group, and geometrical isomerism) is **Option B**: CH3-CH=CH-OH.

### Final Answer:
The required organic compound is **Option B: CH3-CH=CH-OH**.