In the period after 1900, the role of the state in the economy varied, with many states adopting policies to control or manage their economies. Its supposed to be an essay and I don't know how to answer. Help???

Which of the following is an example of negative reinforcement? a. marty knocks over his mother's prize fern so she gives him a time out. b. gwen mows the lawn and her dad takes her out for ice cream. c. tara takes an aspirin, and her headache begins to go away. d. peter comes in late from his lunch and is fired from his job.

Marie places her house plant near a window. the sun shines in the window, but her plant is slightly out of reach for the sun. what will marie's plant do to survive

How do astronomers measure the amount of dark matter in the universe