Final answer:
The language of the Houyhnhnms in Gulliver's Travels is best described as spoken and not written. Their communication reflects their rationality and their societal emphasis on truth without the complexities found in human languages.
Step-by-step explanation:
The language of the Houyhnhnms in Gulliver's Travels is distinguished by its rationality and lack of lies or false representation, which is reflected in the simplicity and directness of their communication. The correct description of the language of the Houyhnhnms is that it is spoken and not written. The Houyhnhnms, being rational horses, have no need for written language, and their communication is based entirely on the spoken word. In contrast to the complexities of human language that include idioms, sarcasm, deceptions, and a vast vocabulary, the Houyhnhnms' language is straightforward. It embodies their societal structure, which places value on truth and reason.
It is important to note that English and other human languages typically contain a large number of words and rules of grammar and spelling, as shown in the examples of the English alphabet which includes vowels and consonants, making up over 600,000 recognized English words according to the OED Online 2011. Additionally, the concept that all language systems contain basic elements like object, subject, action, despite differing in symbols and sounds, further contrasts with the Houyhnhnms' method of communication which excludes the need for written language.