Meaning: 'Complex' means consisting of many different and connected parts, indicating that the communication system is not simple.

Wrong options:

• distant: Distant is an adjective that describes something far away, which does not fit as it does not describe the nature of the communication system.
• ranging: Ranging is a verb that implies variation or extent, which does not appropriately describe the communication system in this context.
• round: Round is an adjective that describes shape, which is irrelevant to the description of a communication system.

Correct answer: family

Explanation: The term 'family' refers to the close-knit social structure of elephants. It fits grammatically as a noun that serves as the object of the preposition 'their' and contextually highlights the importance of familial bonds among elephants.

Meaning: 'Family' refers to a group of related individuals, emphasizing the social connections among elephants.

Wrong options:

• distant: Distant is an adjective that describes something far away, which does not relate to the bonds between elephants.
• ranging: Ranging is a verb that does not fit as it does not describe a type of bond or relationship.
• variety: Variety is a noun that refers to different types or kinds, which does not fit as it does not describe a relationship.

Correct answer: variety

Explanation: The word 'variety' indicates a range of different emotions that elephants can express. It fits grammatically as a noun that complements the phrase 'a wide' and contextually emphasizes the diversity of emotions in their communication.

Meaning: 'Variety' means a number of different types or kinds, highlighting the range of emotions expressed by elephants.

Wrong options:

• distant: Distant is an adjective that does not relate to the range of emotions and does not fit grammatically.
• family: Family is a noun that refers to a group of related individuals, which does not fit as it does not describe emotions.
• ranging: Ranging is a verb that does not fit as it does not describe types of emotions.

Correct answer: apart

Explanation: The word 'apart' indicates the distance between elephants as they move away from each other. It fits grammatically as an adverb modifying the verb 'move' and contextually describes the physical separation of elephants.

Meaning: 'Apart' means separated by a distance, indicating that elephants are moving away from each other.

Wrong options:

• distant: Distant is an adjective that describes something far away, which does not fit as it does not describe the action of moving.
• ranging: Ranging is a verb that does not fit as it does not describe the physical separation of elephants.
• round: Round is an adjective that describes shape, which is irrelevant to the context of distance.

Correct answer: sounds

Explanation: The word 'sounds' refers to the auditory signals that elephants use to communicate. It fits grammatically as a plural noun that serves as the object of the verb 'use' and contextually emphasizes the nature of their communication over distances.

Meaning: 'Sounds' refers to auditory signals or noises, highlighting the method of communication used by elephants.

Wrong options:

• distant: Distant is an adjective that describes something far away, which does not fit as it does not describe a type of communication.
• ranging: Ranging is a verb that does not fit as it does not describe the auditory signals used by elephants.
• round: Round is an adjective that describes shape, which is irrelevant to the context of sounds.