It's not hard to envision how all three of these stocks can deliver exceptional growth.What are the best stocks? Usually, the ones that have clear paths to success.Three Motley Fool contributors have identified what they believe are unstoppable stocks to buy in August. And they all happen to be biotech and pharma companies. Here's why they picked Novo Nordisk (NVO -3.75%), Vertex Pharmaceuticals (VRTX -2.24%), and Viking Therapeutics (VKTX -2.93%).There's still plenty more room to growDavid Jagielski (Novo ...