Underline the correct alterntaive:
a) when a conservative force does positivie work on a body, the potential energy of the body increase/decreases/remains unaltered.
work done by a body against friction always results in a loss of its kinetic /potential energy.
c) The rate of change of total momentum of a many-particle system is proportional to the external force/ sum of the internal forces on the system.
d) In an inelastic collision of two bodies, the quantities which do not change after the collision are the total kinetic energy/total linear momentum/total enregy of the system of two bodies.

Explanation

To solve the question, we will analyze each statement and underline the correct alternative based on the principles of physics.

### Step-by-Step Solution:

1. **Statement a**: "When a conservative force does positive work on a body, the potential energy of the body increases/decreases/remains unaltered."
- **Analysis**: When a conservative force does positive work on an object, it means that the object is moving in the direction of the force. In this case, the potential energy decreases because the object is moving closer to the source of the conservative force (e.g., gravitational force). Thus, the correct alternative is **decreases**.

2. **Statement b**: "Work done by a body against friction always results in a loss of its kinetic/potential energy."
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