For the reaction
`4A +B rarr 2C+2D` which of the following statements is not correct:

Options

A. The rate of disappearance of B is 1/4 the rate of disappearance of A
B. The rate of appearance of C is half the rate of disappearance of B
C. The rate of formation of D is half the rate of consumption of A
D. The rates of formation of C and D are equal

Answer

To determine which statement is not correct for the reaction \( 4A + B \rightarrow 2C + 2D \), we need to analyze the rates of disappearance and appearance of the reactants and products involved in the reaction.

### Step-by-Step Solution:

1. **Identify the Reaction and Coefficients**:
The balanced chemical equation is:
\[ 4A + B \rightarrow 2C + 2D \]
Here, the coefficients are:
- For \( A \): 4
- For \( B \): 1
- For \( C \): 2
- For \( D \): 2

2. **Write the Rate Expressions**:
The rate of a reaction can be expressed in terms of the change in concentration of the reactants and products over time. For this reaction, we can express the rates as:
\[ -\frac{1}{4} \frac{d[A]}{dt} = -\frac{1}{1} \frac{d[B]}{dt} = \frac{1}{2} \frac{d[C]}{dt} = \frac{1}{2} \frac{d[D]}{dt} \]

3. **Analyze Each Statement**:
- **Statement A**: The rate of disappearance of \( B \) is one-fourth of the rate of disappearance of \( A \).
- This is correct because the rate of disappearance of \( B \) is indeed one-fourth of the rate of disappearance of \( A \) (since the coefficient of \( A \) is 4).

- **Statement B**: The rate of appearance of \( C \) is half the rate of disappearance of \( A \).
- This statement is incorrect. The rate of appearance of \( C \) is actually twice the rate of disappearance of \( A \) (since the coefficient of \( C \) is 2, while that of \( A \) is 4).

- **Statement C**: The rate of formation of \( D \) is half the rate of consumption of \( A \).
- This statement is correct. The rate of formation of \( D \) is indeed half the rate of consumption of \( A \) (as both coefficients lead to the same conclusion).

- **Statement D**: The rates of formation of \( C \) and \( D \) are equal.
- This statement is correct. The rates of formation of \( C \) and \( D \) are equal because they both have the same coefficient (2) in the balanced equation.

4. **Conclusion**:
The statement that is not correct is **Statement B**: "The rate of appearance of \( C \) is half the rate of disappearance of \( A \)."

### Final Answer:
**The incorrect statement is Statement B.**