Consider following statement
(A) Work done by pseudo force in non-inertial frame itself cannot be positive
(B) Net work done by static friction on the system (consisting surfaces I contact) is always zero
(C) Net work done by Kinetic friction on the system (consisting surfaces in contact) may be positive
(D) Work done by kinetic friction on a body may be positive
Select correct alternative :-

Options

A. A, B and C
B. B and D
C. A, B and D
D. A, B, C and D

Answer

To solve the question regarding the statements about work done by forces, we will analyze each statement one by one.

### Step 1: Analyze Statement (A)
**Statement (A): Work done by pseudo force in non-inertial frame itself cannot be positive.**

In a non-inertial frame, a pseudo force acts on the body opposite to the direction of the acceleration of the frame. The work done by this pseudo force can be positive if the displacement of the object is in the same direction as the pseudo force. Therefore, this statement is **incorrect**.

### Step 2: Analyze Statement (B)
**Statement (B): Net work done by static friction on the system (consisting surfaces in contact) is always zero.**

Static friction does not do work because there is no relative motion between the surfaces in contact. The work done by static friction is zero as long as the surfaces do not slide over each other. Therefore, this statement is **correct**.

### Step 3: Analyze Statement (C)
**Statement (C): Net work done by kinetic friction on the system (consisting surfaces in contact) may be positive.**

Kinetic friction always acts in the direction opposite to the motion of the sliding surfaces. Hence, the work done by kinetic friction is negative, as it opposes the displacement. Therefore, this statement is **incorrect**.

### Step 4: Analyze Statement (D)
**Statement (D): Work done by kinetic friction on a body may be positive.**

As stated earlier, kinetic friction always opposes the motion of the body. Thus, the work done by kinetic friction cannot be positive; it is always negative or zero. Therefore, this statement is **incorrect**.

### Conclusion
Based on the analysis:
- Statement (A) is incorrect.
- Statement (B) is correct.
- Statement (C) is incorrect.
- Statement (D) is incorrect.

Thus, the correct alternative is **(B)**.

---