Select the incorrect statement.

Options

A. Double bond is shorter than a single bond
B. `sigma-`bond is weaker than a `pi-` bond
C. Double bond is stronger than a single bond
D. Covalent bond is stronger than a hydrogen bond

Explanation

To solve the question "Select the incorrect statement," we will analyze each of the provided statements based on the principles of chemical bonding.

### Step-by-Step Solution:

1. **Statement Analysis**:
- **Statement 1**: "A valid double bond is shorter than a single bond."
- **Analysis**: This statement is correct. Double bonds (bond order 2) are indeed shorter than single bonds (bond order 1) due to increased electron density between the two bonded atoms, which pulls them closer together.

2. **Statement 2**: "Sigma bond is weaker than pi bond."
- **Analysis**: This statement is incorrect. Sigma bonds are generally stronger than pi bonds. Sigma bonds are formed by end-to-end (head-on) overlapping of orbitals, which allows for greater overlap and thus stronger bonding. In contrast, pi bonds are formed by sidewise overlapping of orbitals, which results in less overlap and therefore weaker bonds.

3. **Statement 3**: "Double bond is stronger than single bond."
- **Analysis**: This statement is correct. Double bonds have a higher bond order (2) compared to single bonds (1), which means they are stronger due to the presence of an additional bond.

4. **Statement 4**: "Hydrogen bond is stronger than covalent bond."
- **Analysis**: This statement is incorrect. Hydrogen bonds are much weaker than covalent bonds. Covalent bonds involve the sharing of electrons between atoms, while hydrogen bonds are interactions between a hydrogen atom and a more electronegative atom (like oxygen, nitrogen, or fluorine). The strength of hydrogen bonds is approximately 1/10th that of covalent bonds.

### Conclusion:
The incorrect statements are:
- "Sigma bond is weaker than pi bond."
- "Hydrogen bond is stronger than covalent bond."

However, since the question asks for a single incorrect statement, the most direct incorrect statement is:
- **"Sigma bond is weaker than pi bond."**