This question tests your understanding of under-generalization and over-generalization in child language development.

Understanding the Terms:

• Under-generalization: This occurs when a child applies a word to a narrower set of objects than it actually applies to. For example, a child might only use the word "dog" for their own pet dog and not for other dogs.
• Over-generalization: This is when a child applies a word too broadly, beyond its actual meaning. For example, a child might call all four-legged animals "doggie."

Analyzing the Statements:

• Statement I: "A child calling all four-legged animals doggie - under-generalization" is incorrect. This is a classic example of over-generalization, not under-generalization. The child is extending the word "doggie" to a much wider category of animals than it should apply to.
• Statement II: "A child using word 'duck' for only his toy duck - over-generalization" is also incorrect. This is an example of under-generalization. The child is restricting the use of the word "duck" to a specific instance (his toy duck) rather than understanding its broader application to all ducks.

Conclusion:

Both statements I and II incorrectly classify the examples. Therefore, the correct answer is "Neither I nor II."

Why other options are incorrect:

• Option 1: Incorrect because both statements misidentify the type of generalization.
• Option 3: Incorrect because only statement II is wrong; statement I is also wrong.
• Option 4: Incorrect because only statement I is wrong; statement II is also wrong.