Answer:
doubtful-certain
suggest-demand
vacant-full
mellow-tense
Explanation:
An antonym refers to the word which means the opposite.
When two words have the opposite meaning to each other, they are said to be antonyms.
An antonym can be a word or can be a group of words, i.e, in phrases.
In the answer section, the antonym of the given words has been written. They mean opposite to the word given.
Certain is the antonym of doubtful.
Demand is the antonym of suggest.
Full is the antonym of vacant.
Tense is the opposite of mellow.
