Question 27: The correct answer is B. "was elected." This tense is appropriate for describing an event that occurred in the past, specifically in the context of the history of Finland.

Question 28: The correct answer is D. "is believed." This option correctly uses the passive voice to convey the idea that China is currently believed to have extensive petroleum reserves.

Question 29: The correct answer is A. "was dismissed/has been." This choice correctly combines the past tense "was dismissed" with the present perfect tense "has been" to indicate a past action with relevance to the present.

Question 30: The correct answer is C. "arrived/had been occupied." This choice uses the past perfect tense "had been occupied" to indicate an action that was completed before another past action, which is appropriate in this context.

Question 31: The correct answer is D. "were imposed/had been obtained." This choice correctly uses the past tense "were imposed" for an action that occurred before another past action, and the past perfect tense "had been obtained" to indicate an action completed before the imposition of sanctions.

Question 32: The correct answer is B. "arrested/were freed." This choice uses the past tense "were freed" to indicate an action that occurred after the past action of being arrested, which is appropriate in this context.

Question 33: The correct answer is D. "are used/are taken." This choice correctly uses the present tense "are used" to describe a habitual action, and the present tense "are taken" to describe another ongoing action.