What is the main idea of the article

Which would be the most credible source for researching the effects of smoking? letter from your grandfather web page about someone’s lung cancer report prepared by a tobacco company research article in a scientific journal

In these frames, the author emphasize the challenges lqbal faced by showing

Based on the cause-and-effect relationship in this sentence, what is the meaning of the word revert? the brownies kali made using a new recipe were too dry, so she reverted to her original recipe. a) to alter or change completely; revise b) to dispose of or remove; to throw away c) to prepare for something; assemble or make d) to go back to a previous state or practice