Euphonic? Why?
Japanese verbs undergo some euphonic changes to join to “て” etc. Similarly when an adjective joins to “ございます”, some euphonic changes will be needed. In the past papers of JLPT, such kind of questions have appeared several times. “ございます” is one of Japanese suffix to show “politeness” which is common in service industries. Nowadays some Japanese feel this kind of politeness is too grandiose (大袈裟) for daily usage, thus becoming less popular. Anyway, it is better to have a look in case you are sitting for the JLPT.
Euphonic? How?
きたない (Dict Form)
↓
きたな (Dict Form w/o い)
↓
きたの (な becomes の)
↓
+ う + ございます
↓
きたのうございます (Grandiose Form)
ありがたい (Dict Form)
↓
ありがた (Dict Form w/o い)
↓
ありがと (た becomes と)
↓
+ う + ございます
↓
ありがとうございます (Grandiose Form)
おおきい (Dict Form)
↓
おおき (Dict Form w/o い)
↓
おおきゅ (き becomes きゅ)
↓
+ う + ございます
↓
おおきゅうございます (Grandiose Form))
おいしい (Dict Form)
↓
おいし (Dict Form w/o い)
↓
おいしゅ (し becomes しゅ)
↓
+ う + ございます
↓
おいしゅうございます (Grandiose Form)
さむい (Dict Form)
↓
さむ (Dict Form w/o い)
↓
さむ + う + ございます
↓
さむうございます (Grandiose Form)
ひろい (Dict Form)
↓
ひろ (Dict Form w/o い)
↓
ひろ + う + ございます
↓
ひろうございます (Grandiose Form)