Read the excerpt from the evolution of useful things. but since it is 3m's policy (and that of other enlightened companies) to allow its engineers to spend a certain percentage of their work time on projects of their own choosing, a practice known as "bootlegging," fry was able to gain access to the necessary machinery and materials and to spend nearly a year and a half experimenting and refining his idea for sticky – but not-too-sticky – slips of paper that could be used for "temporarily permanent" bookmarks and notes. which statement best describes the relationship of ideas in this text? a cause-and-effect relationship is signaled by the words "but since." a cause-and-effect relationship is signaled by the words "their own choosing." the passage of time is signaled by the words "of their work time." the passage of time is signaled by the words "a practice."

The correct answer is "A cause-and-effect relationship is signaled by the words "But since." To understand this answer it's important to know the meaning of a cause and effect relationship. This is a relationship in which one event (the cause) makes another event to happen (the effect). When we want to use a cause-and-effect relationship in English we will use sentence connectors as "for, because, therefore, since, as a result of, consequently" In this case we have that because of the 3M' policy there is an effect on the engineers work, it change to a different practice know as "bootlegging." and then Fry was able to experiment and work in his own project. Here "But since" act as a connector to indicate that we have the cause (3M's policy) and then the effect (Fry was able to...)

In other words, we have here  a combination of action and the reaction. We can't see that relationship in the words "their own choosing" because that part is used to explain that engineers can choose their projects due to the 3M's policy. Also when we talk about the relationship of ideas we have a common relationship as examples, cause and effect, contrast-compare and an addition of information techniques. The passage of time here is not relevant because it doesn't connect the ideas to give them meaning but cause and effect does.

A cause-and-effect relationship is signaled by the words "But since."

for the comment!