My English lesson is at 1 o'clock and test is at 2 o'clock.

English Lesson Timing

The question is asking to fill in the blank to indicate a sequence of events. The options are 'now', 'there', and 'then'. Since the English lesson is at 1 o'clock and the test is at 2 o'clock, the word 'then' logically connects these two events in time.