Which of the following statements is incorrect regarding mass?

Options

A. it is a basic property of matter.
B. The SI unit of mass is kg.
C. The mass of an atom is expressed in u.
D. It depends upon the temperature, pressure or location of the object in space.

Explanation

To determine which statement regarding mass is incorrect, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Analyze the First Option**:
- The statement is that mass is a basic property of matter.
- **Evaluation**: This is true. Every piece of matter has mass and occupies space, making it a fundamental property.

2. **Analyze the Second Option**:
- The statement is that the SI unit of mass is kg (kilogram).
- **Evaluation**: This is also true. The kilogram is indeed the standard unit of mass in the International System of Units (SI).

3. **Analyze the Third Option**:
- The statement is that the mass of an atom is expressed in U (atomic mass unit).
- **Evaluation**: This is true as well. Atomic mass is commonly expressed in atomic mass units (U), where 1 U is defined as one twelfth of the mass of a carbon-12 atom.

4. **Analyze the Fourth Option**:
- The statement is that mass depends upon the temperature, pressure, or location of the object in space.
- **Evaluation**: This statement is incorrect. Mass is an intrinsic property of matter and does not change with external conditions such as temperature, pressure, or location.

### Conclusion:
- The incorrect statement regarding mass is the fourth option, which claims that mass depends on external factors.

### Final Answer:
The incorrect statement regarding mass is: "It depends upon the temperature, pressure, or location of the object in space."

---