Concept:Word stress refers to the syllable that is pronounced with greater force or emphasis.Explanation:The word discover is stressed on the second syllable: /dɪsˈkʌv.ə/.The word pertinent is stressed on the first syllable: /ˈpɜː.tɪ.nənt/.The word retrospect is stressed on the first syllable: /ˈret.rə.spekt/.The word penitence is stressed on the first syllable: /ˈpen.ɪ.təns/.Three of the words place stress on the first syllable, but discover places stress on the second syllable.Therefore, discover has a different stress pattern.Answer:A. discover