Using more than one verb tense

In July last year, an experiment was set up, in which different groups of participants who had not previously met and who had not received any preparation, answered questions while they were dealing with a number of different tasks. Pay particular attention to your use of tenses when you are using two or more verbs in the same sentence. Look at the verb tenses in bold in these incorrect sentences from reports on research. 1 Incorrectly mixing past and present tenses The groups went into separate rooms so that they can’t hear each other. What’s wrong: The first verb is in the past and so the second verb must also be in the past. The groups went into separate rooms so that they couldn’t hear each other. To describe how this experiment works in general, however, you could use the present for both verbs: In this experiment, the groups go into separate rooms so that they can’t hear each other. Describing one past action that followed another past action Once they completed the tasks in Room A, the groups went into Room B. What’s wrong: The past perfect, describing an earlier action that allows a second action to happen, should be used in the first part of the sentence: Once they had completed the tasks in Room A, the groups went into Room B.