The correct answer is:

A. smart little Japanese

Explanation:

When using multiple adjectives before a noun, they typically follow a specific order in English:

1. Opinion (e.g., smart, beautiful, interesting)
2. Size (e.g., little, big, small)
3. Age (e.g., old, young)
4. Shape (e.g., round, square)
5. Colour (e.g., red, blue)
6. Origin (e.g., Nigerian, Japanese, French)
7. Material (e.g., wooden, metallic)
8. Purpose (e.g., cooking pot, running shoes)

In the given sentence:

• "smart" (opinion) comes before
• "little" (size), and
• "Japanese" is the performs the function of a noun in this sentence. 

This follows the correct adjective order, making A the correct choice.