Answer:
A. A + B + C --> D
Explanation:
Step 1: A + B --> X (fast)
Step 2: X + C --> Y (slow)
Step 3: Y --> D (fast)
To obtain the overall reaction, we have to sum up the reactants and products of all step and eliminate the intermediates.
Reactants:
A + B + X + C + Y
Products:
X + Y + D
So we have;
A + B + X + C + Y --> X + Y + D
Upon elimination of intermediates, we have;
A + B + C --> D
The correct option is A.
