Question

his speech has become ((increasingly)) slurred. {state the word class of underlined word}

Answer 1

The word class is often referred to as 'part of speech' in the classrooms. Anyhow, the word increasingly is an adverb which is modifying the effect of the quality of the verb- 'speech'.

Below, I have explained "why so?" through the common definition of 'adverbs'.

An adverb is the word which is utilized to provide knowledge about the adjective, verb, or some other adverb. They generally make the presence of the verb or adjective weaker or stronger. (the case is same here). However, they are often put in between the verb and the subject. Other than that, the suffix 'ly' also suggests that the word being asked about is an adverb.

Answer: Word class of increasingly is: Adverb.