19. When Lois sees Clark looking at the TV in shock during Vatman, she realizes this is the first time she has seen Superman and clark at the same time. Initially this does not clue her in, because of course she sees them both, so Clark cannot be Superman. However once she realizes that there is a Superman clone, she puts two and two together, and realizes that Clark is Superman, and that was the clone doing the rescue in Paris.
20. Lois walks in on Jonathan ironing Superman's cape in "Chi of Steeel" and pressures Clark into admitting that he is Superman.
21. In Top Copy Lois notices that Superman is not in focus, and realizes that he is a hologram, and then confronts Clark and gets him to admit that he is Superman.
