... were used to capture the image, and by the way, they had to be used almost immediately after their exposure to the iodine. So, the image on the plate was then exposed to light for ten to twenty ... counseling to the man, it may be concluded that the main topic is the advantages of career counseling for the man. Choices (A) and (C) are mentioned in reference to the main topic, " ;the advantages ... was the substance used for sensitizing the plates, not for fixing the images. Choice (C) is not correct because mercury vapor was the substance used to develop the plates, not to fix the...