Collision theory is `underline("not satisfactory ")`for bimolecular reactions.

Explanation

### Step-by-Step Solution:

1. **Understanding Collision Theory**:
Collision theory states that for a reaction to occur, reactant molecules must collide with sufficient energy and proper orientation. This means that two conditions must be satisfied:
- The colliding molecules must have energy greater than or equal to the threshold energy.
- The molecules must collide in the correct orientation to allow the reaction to proceed.

2. **Bimolecular Reactions**:
...