The following explains why the other choices are wrong:
A) “One another” is erroneous since it suggests that the uniform and hair actively highlight one another, which is not the intended meaning. To demonstrate a reciprocal relationship, the pronoun “each other” is appropriate.
C) The sentence “His white hairs” is grammatically wrong. Although “hair” can be counted (a strand of hair), the singular form “hair” is used here to refer to his entire head of white hair.
D) The phrase “each other of” is grammatically wrong. Here, the preposition “of” is superfluous. “Each other” already communicates the mutually beneficial relationship.
The following explains why the other choices are wrong:
A) “One another” is erroneous since it suggests that the uniform and hair actively highlight one another, which is not the intended meaning. To demonstrate a reciprocal relationship, the pronoun “each other” is appropriate.
C) The sentence “His white hairs” is grammatically wrong. Although “hair” can be counted (a strand of hair), the singular form “hair” is used here to refer to his entire head of white hair.
D) The phrase “each other of” is grammatically wrong. Here, the preposition “of” is superfluous. “Each other” already communicates the mutually beneficial relationship.