Step 1: Understanding the Concept:
Spelling tests assess knowledge of standard English prefixes, suffix roots, and vowel placement.
The target word is an advanced formal adjective meaning causing harm or damage.
It originates from the classical Greek word {dēlētērios} (meaning noxious or destructive).
Success in spelling requires recognizing the syllabic breakdown of complex words.
Step 2: Detailed Explanation:
Let’s break down the precise syllabic construction of the correct term to understand why ``Deleterious'' is the only right answer.
The word is assembled in four distinct vocal beats: De - le - te - ri - ous.
Notice that the first three syllables are consistently anchored by the vowel character 'e':
1. De- (1st syllable)
2. -le- (2nd syllable)
3. -te- (3rd syllable)
It concludes with the standard structural descriptive adjective suffix ``-ous''.
Combining these phonetic blocks gives the layout: D-E-L-E-T-E-R-I-O-U-S.
Let’s review the breakdown errors in the other choices:
$\bullet$ Option (a) Deliterious: This incorrectly swaps the second 'e' for an 'i'.
$\bullet$ Option (c) Deletearious: This introduces an incorrect letter 'a' before the suffix, which is phonetically unnecessary.
$\bullet$ Option (d) Delaterious: This incorrectly substitutes an 'a' in the second syllable instead of an 'e'.
Hence, option (b) is the only authentic spelling recognized in standard English dictionaries.
Step 3: Final Answer:
By following the pattern of triple 'e's in the first three syllables, we confirm the correct spelling.
The correctly spelt word is Deleterious (Option b).