Which options describe a pronoun shift?

A pronoun shift refers to a situation where the pronoun used in a sentence does not agree in number or person with its antecedent or the noun it is referring to. Here are some options that describe a pronoun shift:

1. Singular to Plural Shift: This occurs when a pronoun switches from referring to a singular antecedent to a plural antecedent, or vice versa. For example:
- Incorrect: Each student must submit their own assignments. (singular 'Each' should use 'his' or 'her')
- Correct: Each student must submit his or her own assignments.

2. First Person to Third Person Shift: This happens when the pronoun changes from referring to the speaker (first person) to referring to someone else (third person) without any logical reason. For example:
- Incorrect: I think they should consider if he wants a new job. (either use 'I think he should consider if he wants a new job' or 'I think they should consider if they want a new job')

3. Person Shift: This takes place when there is a change in the subject of the sentence, leading to a pronoun that does not match the new subject's person. For example:
- Incorrect: Sarah loves playing tennis, and they are very good at it. (use 'she' instead of 'they')

4. Ambiguous Shift: This occurs when the pronoun lacks clarity and can refer to multiple antecedents or nouns in the sentence, making it unclear which one it is actually intended to represent. For example:
- Incorrect: John and Sam went to the park, and he brought a frisbee. (it is unclear whether 'he' refers to John or Sam)

Remember, maintaining consistency and agreement between pronouns and their antecedents is important for clear and grammatically correct sentences.