Parts of Speech Questions

In which of the following sentences is the word 'अच्छा' used as an adjective (विशेषण)?

How many types of Avyaya (indeclinable words) are there in Hindi?

Identify the specific class/type of Avyaya (indeclinable word) used in the sentence: 'वह लाचार है, क्योंकि वह अंधा है।' (He is helpless, because he is blind.)

निम्नलिखित में से कौन-सा अव्यय का भेद नहीं है?

In the following passage, some of the words have been left out. Read the passage carefully and select the correct answer for the given blank out of the four alternatives.
The abuse of phrases and the misuse of words rife among us can be checked __________ diligent exercises in good English, such as this book provides. __________ others to be found in different volumes by the same author, will serve to correct careless diction and slovenly speech, and lead to the art of speaking and writing correctly; for, after all, __________ in the use of words is more a matter of habit than of theory, and once it is acquired it becomes just as easy to speak or to write good English __________ bad English.

For the fourth blank: "after all, __________ in the use of words"

What part of speech is the word 'Adjective' itself?