Fill in the blank with the most appropriate word.
My coffee is ____ hot that I can't drink it.
An adverb is a word or phrase that qualifies or changes an adjective, verb or another adverb, to express a relation of a situation, cause etc.
The correct answer is C)so as it indicates the extent (to which her coffee is hot).
Options A, B, and D are wrong as they indicate a greater extent, a lot, and something in addition respectively.
My coffee is so hot that I can't drink it.