In which one of the following sentences is but used as a preposition?

a. i would like to return to italy, but i have no money.
b. i wanted to leave, but i was embarrassed to do so.
c. the lake is pretty, but it's too cold for swimming.
d. we discovered that candy will do anything but work.

(1) fire extended humans’ geographical boundaries by allowing them to travel into regions that were previously too cold to explore. (2) it also kept predators away, allowing early humans to sleep securely. (3) fire, in fact, has been a significant factor in human development and progress in many ways. (4) other obvious benefits of fire are its uses in cooking and in hunting. (5) probably even more important, however, is that learning to control fire allowed people to change the very rhythm of their lives. (6) before fire, the human daily cycle coincided with the rising and setting of the sun. (7) with fire, though, humans gained time to think and talk about the day’s events and to prepare strategies for coping with tomorrow. the sentence that expresses the main idea is: (type the number of the sentence. then click “go.”)

Which statement best explains the function of the subtitlein this text? a.it provides additional information that narrows the focusof the text.b.it draws attention to important information in the table ofcontents.c.it introduces the various sections that appear withineach chapter.d.it explains the author's primary reason for writing aboutthis topic.correct (a)

Which secondary effect of advertisement happens when a customer is satisfied by a product and buys it for a second time?