The weakest form of cohesion is

coincidental
functional
logical
communicational

The correct answer is A. coincidental.

Cohesion is the use of language to connect the ideas in a text. It can be achieved through a variety of means, including repetition, pronouns, conjunctions, and transition words.

Coincidental cohesion is the weakest form of cohesion because it relies on chance rather than intentionality. When two ideas are coincidentally related, it is simply a matter of luck that they happen to occur together. This type of cohesion is often found in casual conversation, but it is not typically used in formal writing.

Functional cohesion is a stronger form of cohesion because it relies on the function of the words in a sentence. For example, a sentence that uses a pronoun to refer to a previous noun is more cohesive than a sentence that does not.

Logical cohesion is the strongest form of cohesion because it relies on the logic of the ideas in a text. For example, a sentence that uses a transition word to show the relationship between two ideas is more cohesive than a sentence that does not.

Communicational cohesion is a type of cohesion that is achieved through the use of nonverbal cues, such as facial expressions, gestures, and body language. This type of cohesion is often used in face-to-face communication, but it can also be used in written communication.