Step 1: Understanding the Concept:
Spray dryer operation depends on particle behaviour.
Velocity and trajectory affect specific parameters.
Step 2: Key Formula or Approach:
No specific formula.
Need to know the factors affecting spray drying.
Step 3: Detailed Explanation:
The velocity of the particle and its trajectory determine the residence time.
Residence time affects the drying process.
Droplet size is determined by atomization.
Weight and shape are determined by other factors.
Thus, residence time is the correct answer.
Step 4: Final Answer:
Velocity and trajectory determine the residence time.
Hence, the correct option is (D).