Step 1: Understanding singular {they.}
Singular {they} is used to refer to a person whose gender is unknown, unspecified, or intentionally not disclosed.
Step 2: Motivation behind option (A).
Using singular {they} avoids the binary and sex-specific pronouns {he} and {she}, making reference more inclusive.
Step 3: Motivation behind option (B).
Gendered pronouns can influence interpretation by foregrounding gender unnecessarily, which singular {they} helps to avoid.
Step 4: Evaluation of remaining options.
Option (C) describes a practical convenience but does not fully explain the broader linguistic motivation.
Option (D) is a sociopolitical claim rather than a linguistic motivation.
Step 5: Conclusion.
Thus, options (A) and (B) correctly explain the motivation for singular {they}.