Final answer:
The question appears to mix elements of English language morphology with terminology typically used in geometry. It addresses English phonetics and orthography, specifically vowels, consonants, and word structures like bases and affixes.
Step-by-step explanation:
This question pertains to letters in words and how they correspond to different sounds or parts of speech, specifically to English phonetics and orthography. To identify which letter corresponds to the base, slant height, or height, one would need to refer to a subject like geometry. However, the question suggests a focus on linguistic elements rather than geometric ones, likely referring to the concept of base letters in English morphology.
The four letters that are always vowels in English are A, E, I, and O. The three letters that can act as vowels or consonants are Y, W, and sometimes U. The base of a word typically refers to the main part of the word without prefixes or suffixes. Regarding the letter C, it is called a soft C when it spells the sound of si as in 'city'.
For example, in the provided analysis, 'Prefixes, Bases, and Suffixes', you can break down words to see their basic parts: a prefix 'P', a free base 'FB', a bound base 'BB', and a suffix 'S'. When dissecting 'spiritual', it's clear that 'spirit' is the base and '-ual' is the suffix. Similarly, 'adventureous' contains the base 'advent' and the suffixes '-ure' and '-ous'.