stress is the degree of force applied when pronouncung the syllable(s) of a word. the stress syllable is the syllable on which the speaker uses more muscular energy and breath effort when pronouncing a word. we have various degrees of stress patterns such as, primary stress, secondary stress, tertiary stress and weakly stressed.
bisyllabic (two syllable) words are usually stressed on the first syllable except the first syllable is a prefix. example (DOCtor) is stressed on the first syllable but ''disprove'' is stressed on the second syllable because the first is a prefix, so it becomes (disPROVE). in the above question, all the options but ''saloon'' have a prefix. that means saloon has its stress on the first syllable.
Note however that, there are certain exceptions to the above rule when the word is either a ''çompound noun'' or a ''compound verb''
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