1. A fish uses its tail for swimming.

2. A fish uses his tail for swimming.
3. A fish uses her tail for swimming.
[Can we use all the expressions, its, his, her?]

4. I have several balls. I have two dogs. The balls are theirs.
5. I have several balls. I have a pet dog. The balls are his.
[Can we use 'theirs' and 'his' in each sentence?]

1. A fish uses its tail for swimming.

2. A fish uses his tail for swimming.
3. A fish uses her tail for swimming.
[Can we use all the expressions, its, his, her?]

4. I have several balls. I have two dogs. The balls are theirs.
5. I have several balls. I have a pet dog. The balls are its.
6. I have several balls. I have a pet dog. The balls are his.
7. I have several balls. I have a pet dog. The balls are hers.
[Can we use 'theirs' and 'its' in each sentence? Can we use his or hers instead of its?]

Yes, all the expressions "its," "his," and "her" can be used to refer to a fish's tail for swimming. The choice of pronoun would depend on the gender of the fish being referred to.

In sentence 4, "theirs" is used correctly to refer to the ownership of the balls by multiple dogs. However, in sentence 5, "his" is not the appropriate pronoun to refer to the ownership of the balls by a single pet dog. Instead, you can use "its" to indicate the possession of the balls by the dog, regardless of its gender.

1. The correct pronoun to use when referring to a fish is "its." Therefore, the sentence should be: "A fish uses its tail for swimming." This is because animals, including fish, are generally referred to by the gender-neutral pronoun "it."

2. Using "his" to refer to a fish is not grammatically correct. While "his" is used to refer to male animals, it is not specifically appropriate for fish. It is more accurate and consistent to use "its" to maintain neutral gender when talking about fish as a species.

3. Similarly, using "her" to refer to a fish is not grammatically correct. While "her" is used to refer to female animals, it is not specifically appropriate for fish. It is more accurate and consistent to use "its" to maintain neutral gender when talking about fish as a species.

4. In the sentence "I have several balls. I have two dogs. The balls are theirs," the pronoun "theirs" is correct to indicate possession by multiple people or animals. Therefore, you can use "theirs" in this sentence to refer to the dogs' possession of the balls.

5. In the sentence "I have several balls. I have a pet dog. The balls are his," the pronoun "his" is correct to indicate possession by a male person or animal. Therefore, you can use "his" in this sentence to refer to the dog's possession of the balls.